# Posts by Dave

Total # Posts: 919

**Biology**

Picks a group of microbes and describes what you envision as a big change/advancement in one aspect relating to that group of microbes in the next five years?

**Math **

"Cab companies often charge a flat fee for picking someone up and then charge an additional fee per mile driven. Pick a U.S. city and research the rates of two different cab companies in that city. Find companies that charge different amounts per mile and have different ...

**Math**

21?

**Math**

Suppose y varies directly with x, and y = 14 when x = -4. What is the value of y when x = -6 How would i do this

**Calculus AB/BC**

Ohh; I see. Thanks!

**Calculus AB/BC**

What's the purpose of finding derivatives? I don't understand why you would need to find a derivative, which is the tangent of the slope of a point on a graph, to find something like "How far did Bob fall". Confusing. Please help. Thank you!

**Math**

1)Susan wants pizza for her birthday party. It costs $8 per pizza plus a $5 delivery fee. She doesn't know how many she needs, so she calculates the price for various numbers of pizza. How would I find out if this is linear or non-linear

**financial management**

a) An investment gives you $10,000 from years 1 through 4 and 40,000 in year 5. If the interest rate is 7.5%, what is the present worth of this investment? (2 points) b)You need $150,000 to buy a new car in 5 years’ time. How much should you save at the end of every ...

**Math**

This is how another person explained it to me: dx/sqrt[(x+1)^2 +4 ] let z = x+1 dx = dz dz/sqrt[z^2 + 4] = ln[z+sqrt(z^2+4)] = ln[x+1 + sqrt(x^2+2x+1 + 4)] because integral dx/sqrt(x^2+p^2) =ln[ x +sqrt(x^2+p^2)] I still don't get how the 1/2 disappeared?

**Math**

Solve the indefinite integral of 1/sqrt(x^2+2x+5). I solved it all out by completing the square and then trig sub and then drawing a triangle to go back to x variable and got: ln |(sqrt(x^2+2x+5)/2 + (X+1)/2 ) | but the book answer is: ln |(sqrt(x^2+2x+5) + x + 1 ) | So, how ...

**Math**

Solve the indefinite integral of 1/sqrt(x^2+2x+5). I solved it all out by completing the square and then trig sub and then drawing a triangle to go back to x variable and got: ln |(sqrt(x^2+2x+5)/2 + (X+1)/2 ) | but the book answer is: ln |(sqrt(x^2+2x+5) + x + 1 ) | So, how ...

**Math**

This is how another person explained it to me: dx/sqrt[(x+1)^2 +4 ] let z = x+1 dx = dz dz/sqrt[z^2 + 4] = ln[z+sqrt(z^2+4)] = ln[x+1 + sqrt(x^2+2x+1 + 4)] because integral dx/sqrt(x^2+p^2) =ln[ x +sqrt(x^2+p^2)] I still don't get how the 1/2 disappeared?

**Math**

I don't understand what you mean?

**Math**

Solve the indefinite integral of 1/sqrt(x^2+2x+5). I solved it all out by completing the square and then trig sub and then drawing a triangle to go back to x variable and got: ln |(sqrt(x^2+2x+5)/2 + (X+1)/2 ) | but the book answer is: ln |(sqrt(x^2+2x+5) + x + 1 ) | So, how ...

**Math**

Evaluate the integral of (e^2x)*sin^3 x dx I let u = e^2x, du = (1/2)e^2x dx v= (-1/3)cos^3 x , dv =sin^3 x dx When I used integration by parts and solved it all out I got: (37/36)intgral of (e^2x)*sin^3 x dx = (-1/3)(e^2x)*cos^3 x + (1/18)(e^2x)*sin^3 x However, the answer ...

**Math**

Evaluate the integral of x*ln(1+x) dx by first making a substitution and then using integration by parts. I let u=1+x and du = dx but then ln(u) du can't integrate to anything?

**Math **

Evaluate the integral from [sqrt(pi/2), sqrt(pi)] of x^3*cos(x^2) by first making a substitution and then using integration by parts. I let u = x^2 and du= 2x dx but then it doesn't equal that in the equation?

**Math**

I appreciate your kindness! Calc II is really a hard subject for me.

**Math**

Solve the integral from [0,pi] of x*sinx*cosx*dx I don't understand how to solve this problem because if I let u =x and du =1 and dv=sinx*cosx, I can't find v. How do you solve this?

**Math**

Thank you so much for your help!

**Math**

Sorry about that, it just says to solve it and the problem didn't say that you need u sub for it. However I still don't know what to let u and dv be?

**Math**

Solve the integral of (x*e^2x)/(1+2x)^2 by first using u substitution and then use integration by parts. I am very confused on how to do u-substitution with this because no mattter what I let u be equal to the du never comes out to be anything in the equation? The correct ...

**Chemistry**

What is traveling faster, an x-ray wave or a radio wave? The question is so general, so how am I suppose to figure it out without any additional information? That is question #7 on our worksheet. Question #4 says how many times more energy is there in one photon of an x-ray ...

**Chemistry **

A 10.0000 g block of aluminum is heated and placed in a stream of oxygen gas, resulting in the formation of aluminum oxide on the surface of the block. The block is cooled and weighed and found to have a mass of 11.6471 g. The block is then placed in a weak acid to remove the ...

**Chemistry**

I don't understand what you mean? I really need to know the values of aluminum and oxygen to solve the problem. I guessed that Aluminum Oxide is 3.5 g and oxygen is 1.6471 g and Aluminum is 1. Something.

**Chemistry**

A 10.0000 g block of aluminum is heated and placed in a stream of oxygen gas, resulting in the formation of aluminum oxide on the surface of the block. The block is cooled and weighed and found to have a mass of 11.6471 g. The block is then placed in a weak acid to remove the ...

**Math**

Evaluate the integral of 1/(1+sqrtx)^4 from [0,1] I started off letting u=1+sqrtx and du=1/2sqrtx, but then there is no 1/2sqrtx in the equation. What am I suppose to do next? The answer in the book is 1/6.

**Math**

Evaluate the integral of (e^z + 1)/(e^z + z) from [0, 1] How do you know what to let equal to u to start this process? The answer in the book is ln(e+1).

**Math**

Evaluate the integral of x * sqrt(x-1) from [1,2]. I let u=x-1 and du=1*dx, but then I can't get rid of the x to start integrating? The answer in the book is 16/15.

**Math**

Evaluate the integral of (x^3 + x^4*tanx) from [-pi/4, pi/4] How do we know which one to let equal to u in order to start this whole process? The answer in the book is 0.

**Math**

Evaluate the integral of e^(1/x) / x^2 from [1,2]. I let u =1/x, but then I am stuck because I am not sure what is the derivative of 1/x is? The answer in the book is e- sqrt(e)

**Math**

Evaluate the integral of x*(2x+5)^8*dx I let u=2x+5 and du=2*dx, but then where do I go from there because I can't get rid of the x in order to integrate?

**Math**

Evaluate the integral of (sin 2x)/(1+cos^2 x) 1. u=cosx and du=-sinx *dx 2. evaluate the integral of -1/(1+u^2)*du 3. result is -ln(1+u^2)+C Where did the sin2x dissapear too???

**Math**

Evaluate the integral of 5^t * sin (5^t) *dt I started out with u = 5^t , but then I got stuck on du because I am not sure how to take the derivative of 5^t? The answer from the book is (-1/ln5) cos(5^t) + C I understand the part with the antiderivative of sin being -cos, but ...

**Math**

Evaluate the integral of (secx)^2 * (tanx)^3 *dx I started out with letting u=secx and du=secx*tanx*dx , but then I am kind of stuck because I don't know how to factor out just secx*tanx? The answer in the book said that it is (1/4)(tanx)^4 + C.

**Trignometry**

Use the appropriate reciprocal identity to find the approximate value of sin ? for the given value of csc ?. Use a calculator. csc ? = 2.15750581

**Trignometry**

Find the exact value of tan ??, given that sin ? =1/2 and ? is in quadrant II. Rationalize denominators when applicable.

**Physics**

A runner is jogging at a steady 3.9 km/hr. When the runner is 7.4 km from the finish line, a bird begins flying from the runner to the finish line at 19.5 km/hr (5 times as fast as the runner). When the bird reaches the finish line, it turns around and flies back to the runner...

**Ed Tech**

To edit the text in a smartart graphic, what must be done first ?

**Parenting**

1. Why is it important to learn about parenting? 2. To what extent does the average person know about child development and parenting? 3. What are some things most parents don’t know about parenting, but maybe should?

**Vectors**

the point (3,-4,5), (1,0,5), and (3,1,-2) are three out of four vertices of a parallelogram ABCD. Explain why there are three possibilities for the location of the fourth vortex, and find the point?

**pre-calculus**

I have absolutely no idea even where to start. Please help! The carnival has come to town with a ferris wheel that has a radius of 30 feet. People get on when passenger compartments are at the lowest, 2 feet off the ground. The wheel makes a full revolution in 20 seconds. ...

**Algebra**

Thank you so much Steve!

**Algebra**

How do you solve sin x * cos x = 1/4 I don't know where to start.

**Algebra**

Given that $x^n - \frac1{x^n}$ is expressible as a polynomial in $x - \frac1x$ with real coefficients only if $n$ is an odd positive integer, find $P(z)$ so that $P\left(x-\frac1x\right) = x^5 - \frac1{x^5}.$

**math**

a rectangular plate 120 ft long and 80 ft wide is submerged vertically with the longer edge in the surface of the water find the force on one side of the plate

**mechanics**

a rectangular plate 120 ft long and 80 ft wide is submerged vertically with the longer edge in the surface of the water find the force on one side of the plate

**Mechanics**

The force Fa=(5i+6j+1k) is applied on a material point while it is shifted by 50m in Oxy plane along a direction 20o CCW versus Ox axis. Find the work done by force on the particle during this shift. The answer should be 337.5J What I did: I found the magnitude of the force: 5...

**Precalculus -- Systems of Equations**

So my final answer would be 8/sqrt(5). Thanks so much!

**Precalculus -- Systems of Equations**

I do not understand this problem. This is part of the question, but I think if I get this part, I'll get the rest. Determine the value(s) of r for which the system: (x^2)+(y^2)=(r^2) x-2y=8 has one real solution. I can't get anywhere! We should solve algebraically...

**Math**

Are you given purple marbles, too?

**chemistry**

A 40.0-mL sample of 0.100 M HNO2 is titrated with 0.200 M KOH. Calculate the volume required to reach the equivalence point (in mL)

**History**

Not c or d well gg

**History**

Well then D

**History**

"When the war ended in 1945, two-thirds of all American men between the ages of 18 and 34 were in uniform. Experts feared that without wartime production, many returning soldiers might have trouble finding jobs. Unemployment would rise, and the economy would tumble."...

**History**

Wiat it's not b it's C

**History**

It's not d or c or a so it's B

**History**

B i think but how would that help in the workplace it's just voting

**History**

Which of the following helped women in the workplace? A the Civil Rights Act of 1964 B the Voting Rights Act of 1965 C the end of segregation D Hernandez v. Texas I think it's D or b

**Chemistry**

Nitrogen monoxide reacts with chlorine gas according to the reaction: 2NO (g) + Cl2 (g) â‡” 2NOCl (g) Kp = 0.27 at 700 K A reaction mixture initially contains equal partial pressures of NO and Cl2 . At equilibrium, the partial pressure of NOCl is 115 torr. What...

**math**

Amy leaves home at the same time every morning and gets to school exactly at 8 AM. If she traveled at 70 meters per minute she would arrive 10 minutes early. If she traveled at 60 meters per minute she would arrive 8 minutes early. What time does Amy leave home each morning?

**Social studies**

B and A

**Social studies**

Which of the following was the main contributor to finally bringing the United States out of the Great Depression? A the National Recovery Administration B the Good Neighbor Policy C wartime spending D the election of Roosevelt D or B ----------------------------------- Which ...

**chemistry**

For the reaction 2Na(s)+Cl2(g)?2NaCl(s)2Na(s)+Cl2(g)?2NaCl(s), how many grams of NaCl could be produced from 20 L of Cl2Cl2 (at STP)?

**Calculus**

The region enclosed by the graph e^(x/2), y=1, and x=ln(3) is revolved around the x-axis. Find the volume of the solid generated. I don't understand if we have to use the washer method or the disk method for this one because when I drew it out on a graph it looked very ...

**Social Studies**

Number 2 only has 1 answer

**Social Studies**

1. Which of the following apply to fascism? Select all that apply. A rooted in militarism B extreme nationalism C respect for minorities D blind loyalty to the state I think its A,B, and c ----------------------------------- 2. Which of the following best describes attitudes ...

**Social Studies**

Which action is often viewed as the most serious attempt to undermine the independence of the judiciary? A President Franklin D. Roosevelt’s plan to reorganize the Supreme Court B appointment of Supreme Court justices to unlimited terms of office C periodic increases in ...

**Social studies**

Lol thx man

**Social studies**

Which of the following factors was most responsible for an unequal distribution of wealth? A There was an increase in business profits. B Wages were not keeping pace with profits of business owners. C Wages were not keeping pace with profits of business owners. D There was ...

**physics**

an object starts from rest and accelerates uniformly to a speed of 100 m s^-1 after 5s. calculate the acceleration of the object.

**math**

Fido weighs 26 pounds more than Fifi. Fifi weighs 12 pounds less than Rover. If the sum of their weights is 71, how much does Fifi weigh?

**Math**

A basket ball team scored a total of 160 points. they made 74 baskets. how many 2 point and how many 3 point shots?

**math**

The perimeter of the isosceles triangle is 28 cm.and side a is equal to (x+2y) while side b is equal to (6y-2x+1) and side c is equal to 4y all in cm.find x and y and hence state the lengths of the side of the triangle

**maths**

whats yearly intrest on 52 grand in a isa at intrest rate 1.5 yearly

**Maths**

If the volume of a cylindrical block is equal to 800cm^3 prove that the total surface area is equal to 2(pi)x^2 + (1600)/x, where x cm is the radius of the base. hence obtain the value x which makes the surface area a minimum.

**Math**

65*50=3250ft^2 so 1625/3250 0.5$/ft^2

**math**

Amy & Ashley bike along the same trail. Amy bikes the entire trail at 20mph & Ashley bikes at 15mph. Amy finishes 8 minutes before Ashley. How many miles long is the trail?

**Chemistry**

Suppose you titrated a sample of sulfuric acid (diprotic acid) with a 0.250 M solution of NaOH. Given the data in the table below, what is the concentration of the sulfuric acid solution?

**Math**

f(x) = cos(x) + 3x Find f^-1 (1) and (f^-1)' (1) f^-1 (1) = 0 (f^-1)' (1) = 1/3 These are the answers given, but I also don't understand how my teacher got these.

**Math**

Actually I do have one question, how do we know that x is 1 already ???

**Math**

Thank You so much!

**Math**

f(x) = x^5 + 2x^3 + x - 1 Find f^-1 (3) and (f^-1)' (3) f^-1 (3) = 1 (f^-1)' (3) = 1/12 Those are the answers, but I have no clue how my teacher got them.

**Math**

lim 200 (30-t)^2 h->0 t=10 The answer should be -8000, but I keep getting -80,000 because I have to do it the long way.

**math**

a truck weighting 20000 pounds going 5 mph what is the force of the truck when it hits a person and comes to a complete stop?

**Math**

There is a graph of a function that looks like y = x^4 , but it has a vertical asymptote at x = -2 and x = 4. The question then asks us to arrange the following numbers in decreasing order: g'(1), g'(-2), g'(0), g'(2), g'(4) I figured out all of the slopes...

**Math**

Is the step function differentiable in its domain? I answered it and said that the step function is not differentiable in its domain because it is not continuous. For the a function to be differentiable it would need to have a value and a limit. However, the step function has ...

**Mats Exercise 1.7**

g (x)= 2\3 (2/3x) (x-2) (x+1)

**Math**

Find the 999th derivative of cos x. I got sin x.

**Math**

lim (cos(π/4 + h) - cos (π/4)) / h h->0

**Math**

lim (cos(π/4 + h) - cos (π/4)) h->0 _________________________ h Somehow I ended up with cos(1).

**Math**

Use the quotient rule to find the derivative of cot x. I tried to solve this, but somehow I got (sec^2x)/(tanx)^2.

**physics**

Identify the force that propels a rocket. 1)The rocket is propelled by the reaction force of the exhaust gasses bouncing off the air molecules outside the rocket. 2)The rocket is propelled because the action force of the rocket on the exhaust gases is greater than the reaction...

**physics**

Identify the force that propels a rocket. 1)The rocket is propelled by the reaction force of the exhaust gasses bouncing off the air molecules outside the rocket. 2)The rocket is propelled because the action force of the rocket on the exhaust gases is greater than the ...

**math**

find the lcm for 6, 18

**History**

What kind of scenes did artists who gained fame tend to paint in the late eighteenth century. Give an example.

**US History**

What kind of scenes did artists who gained fame tend to paint in the late eighteenth century. Give an example.

**Math for Reiny**

your derivative is correct. now just plug in x = π/2 to get the slope remember that tan(π/2) is undefined, BUT cot (π/2) = cos(π/2) / sin(π/2) = 0/1 = 0 so slope = -csc^2 (π/2) = 2 I calculated and got -1 as the slope. Can you please explain how ...

**Math**

Find the inverse of: y = ((-1) / (x+5)) - 1

**Math for Reiny**

your derivative is correct. now just plug in x = π/2 to get the slope remember that tan(π/2) is undefined, BUT cot (π/2) = cos(π/2) / sin(π/2) = 0/1 = 0 so slope = -csc^2 (π/2) = 2 I calculated and got -1 as the slope. Can you please explain how ...