# Posts by ray

Total # Posts: 594

**Math (Stats)**

Well we only use the regression line for predictions if the regression is a reasonable fit for the data, the correlation coefficient is significant, and the data for the predicted values do not go beyond the scope of the data used to estimate the regression. B

*March 11, 2017*

**Math (Stats)**

In order to predict y-values using the equation of a regression line, what must be true about the correlation coefficient of the variables? A. The correlation between variables must be an x-value of a point on the graph. B. The correlation between variables must be significant...

*March 11, 2017*

**Alebra 2**

At what point does the terminal side of the angle (5\pi )/(6) in standard position intersect the unit circle?

*February 14, 2017*

**math **

Elijah made an array of Skittles with 3 rows and 4 columns. Josh made an array of peanuts with 4 rows and 2 columns. Jake made an array of M&M's with 2 rows and 5 columns. What is the total of the candy? -Is it 30?

*February 1, 2017*

**Math**

The population of bacteria in a petri dish doubles every 12 h. The population of the bacteria is initially 500 organisms. How long will it take for the population of the bacteria to reach 800? Round your answer to the nearest tenth of an hour.

*January 31, 2017*

**Math-Geometry**

I am having a difficulty with solving proofs, such as triangle proofs for my homework, is there any tips and tricks to be able to solve them?

*January 29, 2017*

**Math (Octants identifying) *emergency***

How would I identify a set of coordinates (x, y, z) to be in which octant in a 3d space? Is it just based on the x-value? Depending on the x-value (1-8) used?

*January 26, 2017*

**random**

this website is so helpful but i am confused on some things 1) the people who answer questions is this their job or are they volunteering to for free and what do they gain out of this 2)do the tutors who answer questions sit at home and answer or at some work place 3) how ...

*January 22, 2017*

**chemistry**

i thought this was physics

*January 21, 2017*

**Math (misleading graphs) (Statistics)**

Thanks so much!

*January 16, 2017*

**Math (misleading graphs) (Statistics)**

When constructing a graph showing the population of two? countries, an illustrator draws two different people with heights proportional to the populations. Identify a way in which the graph might be misleading. What is the general name for such graphs that use drawings of ...

*January 16, 2017*

**Math (Stats)**

It's C because class limits and class boundaries cannot be the same!

*January 13, 2017*

**Math (Stats)**

What is the difference between class limits and class boundaries? A) Class limits are the numbers that separate classes without forming gaps between them. Class boundaries are the least and greatest numbers that can belong to the class. For integer data, the corresponding ...

*January 13, 2017*

**Computers (RAM) **

Just giving this a shot, Which of the following statements about RAM are TRUE? Select all that apply. a) Any part of RAM can be accessed at any time. b) RAM is an area of a computer that holds programs and data that are waiting to be processed, to be stored on permanent basis...

*January 8, 2017*

**Chemistry (percent abundance) *emergency***

If the average atomic mass of Br is 79.90 amu, what is the percent abundance of each of its isotopes? How would we figure out the isotopes first before we calculate the percent abundance??

*December 12, 2016*

**Math (calculus) (mean values)**

So basically round up this time, wow!

*December 10, 2016*

**Math (calculus) (mean values)**

A company introduces a new product for which the number of units sold Ss given by the equation below, where t is the time in months. s(t) = 155(7-(9/(2+t))) a) Find he average rate of change of s(t) during the first year. I got the answer to be 1395/28 b) During what month of ...

*December 10, 2016*

**Math (optimization) really confused**

Right! Which apparently that isn't the right answer! I did pretty much exactly what @Damon and @Steve but my teacher marked it as wrong. What gives?????

*December 8, 2016*

**Math (optimization) really confused**

A rectangular fenced enclosure of area 225 square feet is divided half into 2 smaller rectangles. What is the minimum total material needed to build such an enclosure?

*December 8, 2016*

**Math (related rates) help?**

Hi there, wouldn't we need to use right triangle trig for this problem since it's asking for the rate of the angle? theta? Not completely sure on how to relate that exactly.

*December 8, 2016*

**Math (related rates) help?**

A 13ft ladder slides down a wall at 2ft/sec when it is 12 ft above the ground. Find the rate at which the angle it makes with the ground changes at this moment?

*December 8, 2016*

**Chemistry (identifying equations)**

What type of reactions are these? Acid-base? Oxidation/Reduction? Precipitation? 1) Zn (s) + 2 HCl (aq) -> ZnCl2 (aq) + H2 (g) 2) Fe (s) + CuSO4 (aq) -> FeSO4 (aq) + Cu (s) 3) Fe (s) + Cu(NO)2 (aq) -> Fe(NO3)2 (aq) + Cu(s)

*December 6, 2016*

**Chemistry (equlibrium direction) urgent**

Consider the endothermic reaction 2 NO(g) <-> N2(g) + O2(g) -If I decrease the volume of the vessel and increasing the total pressure in the vessel, what direction will the equilibrium will shift? (left/right) (I know that decreasing the volume would shift to produce ...

*December 4, 2016*

**Chemistry (molarity) *emergency***

Hi there, maybe dumb question but how would I find the initial concentration of Fe^3+?? In lab, we mixed these reactants into one test tube: -0.50mL of 0.0025M Fe(NO3)3 -0.50mL of 0.0025M KSCN -2.50mL of 0.10M HNO3 The net ionic equation for the experiment is: Fe^3+(aq) + SCN...

*December 3, 2016*

**Math**

On level ground, a 60-foot-tall vertical building casts a 10-foot shadow. at the same time, another vertical building casts a 25-foot shadow. how many feet tall is the second building?

*December 1, 2016*

**physics**

An object of mass 5 kg weighs 30 N on planet Z. The acceleration due to gravity on planet z is? a) 30 m/s^2 b) 10 m/s^2 c) 6 m/s^2 d) 0.17 m/s^2 e) 150 N

*December 1, 2016*

**physics**

It takes 5 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?

*December 1, 2016*

**Chemistry (Molarity) Help**

So there's this prelab assignment we're supposed to complete where we would fill out this table with [FeSCN^2+] in each of the test tubes. I'm not completely sure on how to do this? For example, on the first tube calculate the molarity of [FeSCN^2+] with the data ...

*November 29, 2016*

**Chemistry (Dilution) Help please?**

Calculate how to prepare 100.0mL of a 1.25x10^-4 M aqueous solution of Fe(NO3)3(aq) by dilution of stock of 0.0025M Fe(NO3)3(aq) in a 100.0mL volumetric flask? I tried using the m1v1=m2v2 equation but it doesn't look like that equation would work for this problem??

*November 29, 2016*

**Math (Calculus) (Related Rates)**

A boat pulls away from a dock at 2 m/s, but the operator has neglected to remove the tow rope used to pull the boat up to the dock. This rope runs thru a pulley which is attached to the dock at a point 1 m higher than the point at which the rope is attached to the boat. A) How...

*November 29, 2016*

**Math (Calculus) (Related Rates)**

A boat pulls away from a dock at 2 m/s, but the operator has neglected to remove the tow rope used to pull the boat up to the dock. This rope runs thru a pulley which is attached to the dock at a point 1 m higher than the point at which the rope is attached to the boat. A) How...

*November 28, 2016*

**Math (calculus) (optimization)**

Found the answer, it was a calculator error but r is actually~6.2035 leading h~24.8141

*November 27, 2016*

**Math (calculus) (optimization)**

A solid is formed by adjoining two hemispheres to the ends of a right circular cylinder must have a volume of 4000 cubic feet. The hemispherical ends cost twice as much per square foot of surface area as the sides. Find the dimensions that will minimize cost. I got as far as ...

*November 27, 2016*

**Math (calculus) (mean values)**

Got the same answer, 3.29 which is around march, but that answer was not correct according to the website

*November 27, 2016*

**Math (calculus) (mean values)**

A company introduces a new product for which the number of units sold S is given by the equation below, where t is the time in months. s(t)=155(7-9/(2+t)) a) Find the average rate of change of s(t) during the first year. Which my answer was 1395/28 b) During what month of the ...

*November 27, 2016*

**Algebar**

81x^(6)-25y^(10) Factor

*November 21, 2016*

**Math (Calculus) (mean value theorem emergency)**

b) Using the mean value theorem gave me f'(c)=1 and solving for c gave me 1 as well. c) Tangent line y=x-13 I checked with a graphing calculator and my answers look right

*November 19, 2016*

**Math (Calculus) (mean value theorem emergency)**

Consider the graph of the function f(x)=x^2-x-12 a) Find the equation of the secant line joining the points (-2,-6) and (4,0). I got the equation of the secant line to be y=x-4 b) Use the Mean Value Theorem to determine a point c in the interval (-2,4) such that the tangent ...

*November 19, 2016*

**Math (Differentials)**

Oh! Minor mistake, thanks for the help!

*November 18, 2016*

**Math (Differentials)**

Use differentials to approximate the value of the expression. cube root of 25 I set x=27 and dx=-2 and got ~3.0741, what did I do wrong?

*November 18, 2016*

**Math (equation of tangent line)**

I had that on the back of my head when I was doing this but thought that wouldn't be possible, thanks so much!

*November 17, 2016*

**Math (equation of tangent line)**

Any ideas anyone? I need to have this turned in by tomorrow, any help is greatly appreciated

*November 17, 2016*

**Math (equation of tangent line)**

Maybe my derivative isn't correct in the first place? I used the quadratic formula to solve for x and got x being equal to -1 but when I plug that into the equation I get 0/0, which certainly means I'm doing something wrong. Any ideas?

*November 17, 2016*

**Math (equation of tangent line)**

Consider the implicit equation 2xy-1=(x+y+1)^2 a) Compute and solve for the derivative dy/dx as a function of x and y. b) Find the equation of the tangent line to the graph of the above when y=-1. For part a, I found the derivative being equal -(x+1)/(y+1) but how would I find...

*November 17, 2016*

**Math (Slope of inverse tangent line)**

a) 2 b) 1/2

*November 17, 2016*

**Math (Slope of inverse tangent line)**

Given the graph, goo.gl/photos/VTMjKvNsVvAQwe3X6 a) What is the slope of the tangent line to the graph of f^-1 at the point (-1/2,-1)? b) What is the slope of the tangent line to the graph of f^-1 at the point (1,2)?

*November 17, 2016*

**Science (Stoichiometry with Gasses) (Chemistry)**

If 1.00 kg of methane (CH4) is burned completely (in excess O2) and the CO2 produced is collected at 20°C and 1.00 atm, what volume (L) will this CO2 occupy??

*November 16, 2016*

**Chemistry (Mass/volume)**

What are factors that will contribute to achieving the lowest mass/volume ratio possible for an airbag? The "mass" includes the mass of the reactants, bag, and any additional materials you would use to make the airbag. The "volume" is of the inflated air bag.

*November 15, 2016*

**Math checking answers (Calculus Differentials)**

The radius of a spherical balloon is measured as 8 inches, with a possible error of 0.02inch. a) Use differentials to approximate the possible propagated error in computing the volume of the sphere. b) Use differentials to approximate the possible propagated error in computing...

*November 14, 2016*

**Chemistry (molarity) (sorta an emergency)**

It looks like it's the same answer, but how we got to it was different. With your equation, that's what I would take on for this lab, but my chemistry teacher warned us a million times to NOT do it that way, don't know why, but she wanted us to do it the way I ...

*November 13, 2016*

**Chemistry (molarity) (sorta an emergency)**

I'm doing a titration lab and writing a lab report where I'm sort of stuck on how exactly to find the concentration of HCl. These are the following info I have from the lab, Equation: HCl(aq)+NaOH(aq)-> H2O(l)+NaCl(aq) -Calculated molarity of NaOH solution is .103M...

*November 13, 2016*

**Math (Derivative)**

This leaves with dy/dt=12(-.75/8) dy/dt=-1.125 dy/dt=-9/8

*November 13, 2016*

**Math (Derivative)**

Finally figured out, simply plug the given x value into the original equation!

*November 13, 2016*

**Math (Derivative)**

Assume that x and y are both differentiable functions of t and the required values of dy/dt and dx/dt xy=6 a) Find dy/dt, given x=8 and dx/dt=12 b) Find dx/dt, given x=1 and dy/dt=-8 I started with a and got dy/dt=dx/dt(-y/x) Plugging with the given values leaves me with dy/dt...

*November 13, 2016*

**Chemistry (molarity)**

How would I find the moles of NaOH solution that was used to titrate? I have 20.01mL of HCl used and 15.95mL of NaOH solution was used to titrate.

*November 10, 2016*

**Chemistry (molarity)**

DrBob222 you're exactly right on 2! Sorry my teacher didn't really clarify exactly what was being asked but I took on the question like how #2 is stated, and therefore said that the molarity of the NaOH wouldn't be affected by the amount of water added prior to the...

*November 10, 2016*

**Chemistry (molarity)**

Yes I know the formula of molarity M=mol/L but the volume of water is not accounted for in this calculation specifically since the volume we're using is the volume of NaOH solution dispensed into the flask. Therefore, water shouldn't have an effect on the molarity of ...

*November 10, 2016*

**Chemistry (molarity)**

Btw, KHP is Potassium hydrogen phthalate C8H5KO4

*November 10, 2016*

**Chemistry (molarity)**

What would the effect on your molarity of NaOH be if you had added 35 mL of water to dissolve the KHP (acid) instead of 25 mL? Explain. My answer so far is that adding more water shouldn't affect the molarity at all because water does not account for the reaction between ...

*November 10, 2016*

**Algebra**

I'm trying to rewrite 3x^2*e^-x*tan(4-x) Can I rewrite it as 3x^2*tan(4-x)/e^x ?

*November 3, 2016*

**Algebra**

Just a quick algebra question, if I had (e^x)/(x^3+x^-3) could I rewrite it as : (e^x)+(x^3)/(x^3) ?? (flipped the negative exponent from the bottom and made it positive on top)

*November 3, 2016*

**Chemistry (Concentratrion/molarity)**

A 25.00 mL aliquot of HCl of unknown concentration is titrated with 25.62 mL of 0.1011 M NaOH. What is the molarity of the HCl solution?

*November 1, 2016*

**Chemistry help emergency? (theoretical mass/mol)**

I am supposed to calculate the theoretical mass and moles of Cu. However I am given the mass of 2 reactants in the balanced equation: 3CuCl2*2H2O + 2Al -> 3Cu + 2AlCl3 + 6H2O I am given the mass of CuCl2*2H2O to be 0.477g and the mass of Al is 0.267g. If I wanted to ...

*November 1, 2016*

**Calculus differentiable and continous identify**

1. Which of the above functions are not continuous where they are defined? Why? 2. Which of the above functions are not differentiable where they are defined? Why? Photo Link: goo.gl/photos/2RPU1dAWoKzUn4Pf8 For the first question, I said that graph F is not continuous because...

*October 30, 2016*

**Math (Continuous/Differentiable)**

Any ideas?

*October 30, 2016*

**Math (Continuous/Differentiable)**

goo.gl/photos/2RPU1dAWoKzUn4Pf8 1. Which of the above functions are not continuous where they are defined? Why? 2. Which of the above functions are not differentiable where they are defined? Why? For the first question, I said that graph F is not continuous because of a jump, ...

*October 30, 2016*

**Math Derivative**

Find derivative of f(x)=g(h(x)) Would the derivative be something like: g'(h(x))*h'(x) ??

*October 28, 2016*

**Math (Finding Vertical Tangent)**

Or near x=2, that was pretty easy, can't believe I didn't spot it at first

*October 28, 2016*

**Math (Finding Vertical Tangent)**

At first I said x=-3 but that is a vertical asymptote, not a vertical tangent. Where does this graph have vertical tangents in this case?

*October 28, 2016*

**Math (Finding Vertical Tangent)**

List all x values where the graph of f(x) has vertical tangents goo.gl/photos/iPu1SHA8yyBFTcZj6

*October 28, 2016*

**Math (Derivative)**

Compute derivative using the definition of the derivative. f(x)=1+1/x^2 1+ 1/(x+h)^2 - (1+ 1/(x^2)) ------ divide by h and multiply by reciprocal 1/h(x+h)^2 - 1/hx^2 Next I expanded it and got this messy huge number and multiply the bottom of each other after cancelling some ...

*October 28, 2016*

**Math (Derivative)**

.. the minus made the x from the right side which forces those two to cancel out. I'm totally overlooking this problem than it needs to be. Thanks for helping me clarify a rather simple problem!

*October 27, 2016*

**Math (Derivative)**

Yes I know the definition of the derivative, I think I'm just confused on the algebra part. x+h - 1/(x+h) Just that left side of the equation is where I'm lost. It went from that to h-1/(x+h) Did that x just got canceled out from the left hand side? Other than that, I ...

*October 27, 2016*

**Math (Derivative)**

How did that h on the left right below "subtract" come from??

*October 27, 2016*

**Math (Derivative)**

Computer the derivative of f(x)=x-(1/x) for x>0 using the definition of the derivative.

*October 27, 2016*

**Math (Limits)**

So I can just say for example, plug values as y gets closer to 1 and solve for the function and notice that the function is getting smaller and smaller (negative) and therefore negative infinity?

*October 27, 2016*

**Math (Limits)**

lim ln(y-1) y->1+ The answer is negative infinity but how do I show the logic of proving that it's negative infinity? I plugged in "1" to the function and got ln(0) which is obviously impossible? Thanks in advance

*October 27, 2016*

**Chemistry**

Methane, CH4 is the main component of natural gas which is used for cooking in many homes. The molar heat of combustion of methane is -890kj/mol. A cook wants to boil some water on a gas stove. If the stove burns 5.00g of methane to heat 2575 ml of water, what is the ...

*October 27, 2016*

**Chemistry**

Silicon carbide (SiC) is made by reacting sand (Silicon dioxide, SiO2) with powdered carbon at high temperature. Carbon monoxide is also formed. What is the percent yield if 51.4kg of SiC is recovered from processing 100.0kg of sand? What mass (in kg) of carbon would be needed...

*October 25, 2016*

**Math**

6 softball teams are to play each other once. how many games are needed?

*October 24, 2016*

**Science (Chemistry) (Yield)**

I tried doing some conversion factors and came up with this: (0.101g Mg)(1mol MgO) |(40.31g MgO) ---------------------- (24.31g Mg)|(1mol MgO) =~0.167g MgO as my theoretical yield if I had a mass of 0.101g of Mg Did I do this correctly?

*October 24, 2016*

**Science (Chemistry) (Yield)**

Using your mass of Mg (0.101g), and assuming all of the Mg burns in oxygen and forms the theoretical predicted product, calculate the theoretical yield of magnesium oxide. I wrote out the equation and it turned out to be: 2Mg+O2->2MgO I have my mass of Mg but how do I get ...

*October 24, 2016*

**Physics**

A ball is on the end of a rope that is 1.75 m in length. The ball and rope are attached to a pole and the entire apparatus, including the pole, rotates about the pole's symmetry axis. The rope makes an angle of 78.0° with respect to the vertical. What is the tangential...

*October 23, 2016*

**Chemistry (atoms)**

How many atoms of oxygen, O, are in 0.0595 moles of water?

*October 23, 2016*

**math (horizontal tangent line)**

Determine the point(s) if any at which the graph of the function has a horizontal tangent line. y=x^3+x I graphed this function out and it looks like there isn't any horizontal tangents. Am I correct or am I forgeting something? I tried finding the derivitave of the ...

*October 22, 2016*

**Math (Calculus)**

Determine if each of the following functions is in Big-O, is Big-Omega and is Big-Theta of x: (Could be multiple) a) f(x)=10 b) f(x)=3x+7 C) f(x)=x^2+x+1 d) f(x)=5log(x) e) f(x)=|x| f) f(x)=x/2 I'm in calc 1 and I have no idea what's it even asking me. Help? Thanks in ...

*October 22, 2016*

**Health care tech**

I would say it's all of those. All of your equipment would be useless if there wasn't any software telling them what to do!

*October 21, 2016*

**Math (Calculus)**

Determine if each of the following functions is in Big-O, is Big-Omega and is Big-Theta of x: (Could be multiple) a) f(x)=10 b) f(x)=3x+7 C) f(x)=x^2+x+1 d) f(x)=5log(x) e) f(x)=|x| f) f(x)=x/2 I'm in calc 1 and I have no idea what's it even asking me. Help? Thanks in ...

*October 21, 2016*

**Technology and online learning**

Remember we're looking at its validity of a website. Therefore you wouldn't want biased information. Yeah sure the website may be professional looking, but that doesn't mean that it's valid and genuine. You would want up to date and accurate information instead...

*October 21, 2016*

**Math (Function differentiable)**

Any ideas?

*October 20, 2016*

**Math (Function differentiable)**

Determine whether the function is differentiable at x=2 x^2+1 for x<(or equal to) 2 4x-3 for x>2 I did the math for the limits of both equations and they both approach to 4. So that means they are differentiable right?

*October 20, 2016*

**Math**

The density of water at 21 degrees C is 0.997992 g/mL. The density of water at 22 degrees C is 0.997770 g/mL. What is the density of water if the room temperature is 21.3 degrees C?? So I would just multiply 30 percent of the density at 21 degrees C but I'm stuck on how to...

*October 18, 2016*

**Science (Chemistry) Ratio of mole**

I understand your math, but where did Oxygen started with 2 of them to be O2? Is it because of the charges?

*October 17, 2016*

**Science (Chemistry) Ratio of mole**

You measured out 0.101g of Mg. You heat the sample and measure out 0.234 of the magnesium oxide compound. Given your data, what us the empirical formula for the Mg(x)O(y)? x and y are ratio x:y If I'm doing this correctly, I divided 0.101g of Mg/24.31g of Mg = .00415 mol ...

*October 17, 2016*

**Math (derivative by limit process)**

Find the derivative of the function by the limit process. f(x)=1/sqrt(x) I've worked through my problem and got f'(x) to be -1/2x but the actual answer is -1/2x^3/2? Where did the 3/2 power come from? Any help is greatly appreciated!

*October 16, 2016*

**AMDM1**

The amount of paint a painter needs is directly proportional to the area of the object he is painting. If a painter needs g gallons of paint for every s square feet that he paints, what is the total amount of paint that he needs to paint a house in terms of g and s?

*October 14, 2016*

**Math (Instanttaneous rate of change)**

I see, this was a lot simpler than I expected! Thanks so much

*October 13, 2016*

**Math (Instanttaneous rate of change)**

Compute the instantaneous rate of change f'(a) for the function f(x) at x=a using: f'(a)=lim(h->0) (f(a+h)-f(a))/h f(x)=x^2 at x=3 My teacher didn't even go over the problem since class was over but gave us the answer being 6. How do you approach this problem to...

*October 13, 2016*

**Math/Chemistry**

Aren't we supposed to multiply 50.0g by 0.001? Where did 1E^-5 come from?

*October 11, 2016*

**Math/Chemistry**

Your friend eats 50.0g tuna steak. You find out that the tuna is 0.001% (by mass) mercury. The lethal dose of mercury is 5.5x10^-3 mg of mercury. Should you take your friend to the hospital?

*October 11, 2016*