Friday

September 4, 2015
Total # Posts: 21,876

**science**

yes, sometimes one moves behind the other, masking the pair look dimmer
*April 9, 2015*

**math**

You are welcome :)
*April 9, 2015*

**math**

I said (1/5) x + 2 = x - 4 multiply everything both sides by 5 x + 10 = 5 x - 20
*April 9, 2015*

**math**

I do not know. Do you mean y=(1/5)x+2 y=x-4 then x + 10 = 5 x - 20 x = 30/4 = 15/2 = 7.5 or do you mean y = 1/(5x) + 2 then 1 + 10 x = 5 x^2 - 20 x solve quadratic or do you mean 1/(5x+2) = x-4 1 = (5x+2)(x-4) 1 = 5 x^2 + 18 x - 8 etc
*April 9, 2015*

**science**

I believe so.
*April 9, 2015*

**calc(steps and explanation also)**

D^2 = x^2 + y^2 2 D dD/dt = 2 x dx/dt + 2 y dy/dt or dD/dt = (x dx/dt + y dy/dt)/D at t = 0 x = 0 y = 150 at t = 10 x = 580 y = 150+100 = 250 D = sqrt(580^2+250^2) = 631.6 dx/dt = 58 dy/dt = 10 so plug into dD/dt = (x dx/dt + y dy/dt)/D
*April 9, 2015*

**math**

12 x - 3 = 2 x + 4 10 x = 7 x = 7/10 y = 2(7/10) + 4 y = 14/10 + 4 y = 5.4
*April 9, 2015*

**math**

600 = 5 n + 10 d + 25 q n = 10 d + q = 25 600 = 50 + 10 d + 25 q or 550 = 10 d + 25 q or 110 = 2 d + 5 q so 2 d + 5 q = 110 2 d + 2 q = 50 ---------------- 3 q = 60 q = 20 you take it from there.
*April 9, 2015*

**Calculus**

angle a = tan^-1 (.5) da/dt = -.25 deg/min = -.009436 radians/min x = 25 = y tan a y = 25/tan a dy/dt = -25 sec^2 a da/dt /tan^2 a
*April 9, 2015*

**physics**

F = 2.51 (9.81) - 3.08 (9.81) sin 32.3 = 8.48 N a = F/m = 8.48/(2.51+3.08) 2.51(9.81) - T = 2.51 a
*April 8, 2015*

**calculus**

feet, yuuk :( oh well, g = 32 ft/s^2 in that case Vi = 42 sin 16 = 11.6 ft/s u = 42 cos 16 = 40.4 ft/s Horizontal problem: goes 20 ft at 40.4 ft/s t = 20/40.4 = .495 s Vertical problem with t = .495 s -m g = m d^2h/dt^2 d^2 h/dt^2 = -g = -32 dh/dt = Vi - 32.2 t h = Hi + Vi t...
*April 8, 2015*

**math /fraction**

HUH? (1/3)(12) = 4
*April 8, 2015*

**calculus**

draw a picture ! (a) 5*2 = 10 4 + 10 = 14 (b) 2 * 4 = 8 Unless I am missing something :)
*April 8, 2015*

**calculus**

v = (1/3) base area * height for anything pointy with straight sides slant height = R cut away sector angle a sector angle remaining = 2pi-a base radius remaining =r= 2piR(2pi-a)/2pi = R(2 pi-a) height h = sqrt(R^2-r^2) v = (1/3)(pi r^2)h plug and chug
*April 8, 2015*

**Calculus (urgent help)**

http://www.jiskha.com/display.cgi?id=1428548293
*April 8, 2015*

**serious reply**

29 *47 ------ ones * ones 7*9 = 63 ones * tens 7*20 =140 tens * ones 40*9 = 360 tens * tens 40*20 = 800 add = 1363
*April 8, 2015*

**chemistry**

Mercury sulfide Chemical Compound Mercury sulfide, mercuric sulfide, mercury sulphide, or mercury sulfide is a chemical compound composed of the chemical elements mercury and sulfur. It is represented by the chemical formula HgS. "******It is virtually insoluble in water...
*April 8, 2015*

**Exponential Equations**

It doubles ten times t x 0 1000 18 2000 one time 36 4000 2 times 54 8000 3 times 72 16000 4 times or 1000*2^4 90 108 ...... 180 1024*1000 = 1,024,000 = 1000*2^10
*April 8, 2015*

**Math**

24 % of 100 is 24 29 % of 100 is 29 She has 29 from Norway and 24 from France so 29 - 24 = 5
*April 6, 2015*

**algebra**

y = -2 x^3 + b x^2 + c x + d y(0) = 2 so d = 2 y = -2 x^3 + b x^2 + c x + 2 1 = -2 + b + c + 2 or b+c=1 -2 = 16 + 4 b - 2 c + 2 or -20 = 4 b - 2 c or -10 = 2 b - c 2 b - 1 c = -10 1 b + 1 c = 1 ---------------- 3 b = - 9 b = -3 etc
*April 6, 2015*

**Physics**

convert this into a projectile problem. First solve for velocity of projectile needed to reach ground at 10 meters when fired at 45 deg from height of 1 m Call that V1 Now find V2, the new velocity Q2 = .5 Q1 = .5 * V1 * A1 and Q2 = V2 A2 so V2 = .5 V1 (A1/A2) = .5*(1/.2) * V1...
*April 6, 2015*

**physics**

I have no idea. At constant speed propulsion force = drag force and mass is not part of the problem.
*April 6, 2015*

**physics**

gravity p = rho g h
*April 6, 2015*

**physics**

v = 2 - 10 t y = 2 t - 5 t^2 x = 1 t so t = x y = 2 x - 10 x^2
*April 3, 2015*

**calculus**

length = L width = w A = L w cost = 400 = 10(2L+2w) = 20(2w) 400 = 20 L + 60 w 20 = L + 3 w L = 20 - 2 w A = 20 w - 2 w^2 dA/dw = 0 = 20 - 4 w w = 5 L = 10
*April 3, 2015*

**stastic**

Given the following information about a sample, calculate a z score for a test grade of 91. = 87, s = 4.01 (Points
*April 2, 2015*

**Algebra 2**

http://www.easycalculation.com/statistics/standard-deviation.php
*March 31, 2015*

**Algebra 2**

https://www.easycalculation.com/statistics/standard-deviation.php add up the squares of the difference between each value and the mean divide it by 7 or 6 depending on if the population sd or just sd is desired take the square root.
*March 31, 2015*

**physics**

1 hp = 550 ft lbs/s so 25 hp = 13,750 ft lbs/s = Torque *radians/sec 1800 rev/m (2 pi rad/rev)(1 m/60 s) = 188 radians/s so Torque = 13750/188 = 72.9 ft lbs
*March 31, 2015*

**science help.. pls help me dr.bob22 or damon**

In one case it is ionic In the other case it is covalent However In both cases it is chemical
*March 31, 2015*

**science help.. pls help me dr.bob22 or damon**

Water is a covalent bond but a special polarized one called a "hydrogen bond" that results in attraction between water molecules
*March 31, 2015*

**Algebra 2**

If c is the hypotenuse (opposite the right angle) then c^2 = a^2 + b^2 or b^2 = 361 - 9 b = sqrt(352) = 18.8 sin A = a/c sin B = b/c
*March 31, 2015*

**science help.. pls help me dr.bob22 or damon**

I think so.
*March 31, 2015*

**science help.. pls help me dr.bob22 or damon**

I suspect that finding that electrons surround a nucleus would be fatal for the hypothesis of indivisibility :)
*March 31, 2015*

**math - linear equation**

y = x y = -x
*March 31, 2015*

**science help.. pls help me dr.bob22**

been there done that below metals and halogens are likely to form ionic bonds
*March 31, 2015*

**pls help me dr.bob22 science**

Yes Oscar it is B. but you mean Zn + 2HCl = H2 + ZnCl2
*March 31, 2015*

**pls help me dr.bob22 science**

Yes
*March 31, 2015*

**pls help me dr.bob22 science**

If it is an ionic bond it is an ion K+ will do as will F- Cl2 is a complete molecule Ne is a noble gas which is too proud to react much.
*March 31, 2015*

**science help check**

Metals from Group 1 are most likely to form ionic bonds Halogens, group 17, are also likely to form ionic bonds
*March 31, 2015*

**Calculus - all the same question**

If you can follow the one I did, you can do the rest.
*March 30, 2015*

**Calculus**

dC/dx = 100 - .2 x at x = 35 dC/dx = 100 - 7 = 93 dollars per club at a level of 35 clubs by the way total C for 35 clubs = 3877.5 or about an average of 111 dollars per club
*March 30, 2015*

**Chemistry**

one C per molecule? 6.02 * 10^23 molecules per mol 2.46 * 10^25 molecules *(1/6.02*10^23) = 40.9 mols How many grams? 40.9 * (12 + 4(35.5) ) what volume? grams / 2.71 g/mL
*March 29, 2015*

**Differential Calculus**

radius of circle = r side of square = s 10 = 4 s + 2 pi r so s = 2.5 - .5 pi r A = pi r^2 + s^2 or A = pi r^2 + 6.25 - 2.5 pi r + .25 pi^2 r^2 A = (.25 pi +1)pi r^2 -2.5 pi r + 6.25 I am going to use calculus, you can complete the square to find vertex of parabola dA/dr = 0 ...
*March 29, 2015*

**Geometry**

I used 400, use 500
*March 29, 2015*

**Geometry**

2 h + 2 w = 400 h + w = 200 w + 40 + w = 200 2 w = 160 w = 80 h = 120
*March 29, 2015*

**Civics to Ms.Sue**

Ms Sue is completely correct. There were presidents under the Articles.
*March 27, 2015*

**Civics to Ms.Sue**

It did not allow for a Department of Commerce :)
*March 27, 2015*

**Civics to Ms.Sue**

Well, the Articles of Confederation allowed for a president.
*March 27, 2015*

**Algebra 1**

0 = -0.04x^2+1.3x+56 or 0 = 0.04x^2 - 1.3x - 56 solve quadratic
*March 27, 2015*

**us history**

Now why would a state stay in the Union even if some of its residents had slaves? Maybe some of them did not have slaves and disagreed with the others?
*March 27, 2015*

**us history**

I do not think it is b or d
*March 27, 2015*

**Algebra 1**

.04 x^2 - 8.3 x - 4.3 = 0 http://www.webgraphing.com/quadraticequation_quadraticformula.jsp#
*March 27, 2015*

**Algebra 1**

y = x (-.04 x + 8.3) when is y = 0 at the start of course but also when .04 x = 8.3 or x = 207.5 meters I think you left a significant figure out :)
*March 27, 2015*

**Algebra**

y = k/x 300 = k /4 so k = 1200 y = 1200/150 y = 8
*March 27, 2015*

**Algebra**

I bet you mean [ f(x) - f(a) ] / (x-a) Parentheses are VITAL ! f(a) = -2 a^2 + 5 a - 1 so [ -2(x^2-a^2) +5(x-a) -1+1 ]/(x-a) = [-2(x-a)(x+a) + 5(x-a) ]/(x-a) = -2(x+a)+5 Note for future calculus purposes that the limit of this as a approaches a this becomes -4 x + 5
*March 27, 2015*

**us history**

I do physics actually. I just happened to know this.
*March 27, 2015*

**us history**

Jim Crow laws, C is right.
*March 27, 2015*

**Algebra**

distance = pi D in feet = pi * 64 * (1 mile/5280 ft) time = 25 s (1 h /3600 s) divide the distance in miles by the time in hours
*March 27, 2015*

**algebra**

y dy = x dx y^2/2 = x^2/2 + c or y^2 = x^2 + c (-3)^2 = 0 + c so c = 9 y^2 = x^2 + 9 y = +/- (x^2+9)^(1/2) since only y = -3 is given I think your answer correct
*March 27, 2015*

**math**

AB^2 = 64 + 4 = 68 BC^2 = 9 + 9 = 18 AC^2 = 25 + 25 = 50 Note that 68 = 50 + 18 therefore a right triangle
*March 27, 2015*

**physics**

F = m A F = (10.45)(2.5)
*March 27, 2015*

**Economics**

10 years 10.3 = 1.9 (1+r)^10 10 log(1+r) = log(5.42) log(1+r) = .0734 1+r = 1.184 so 18.4 percent per year
*March 27, 2015*

**math**

http://davidmlane.com/hyperstat/z_table.html
*March 27, 2015*

**Pre-Calculus**

Because she used parentheses.
*March 26, 2015*

**Math**

a) .15 * 15 = 2.25 NOT 1 c) correct e) corrtect
*March 26, 2015*

**Math**

b) CORRECT c) .045 * 1000 = 45 CORRECT ! d) NO way, you really feel 45 m is almost half a kilometer? e) 4500 / 1000 = 4.5 meters!
*March 26, 2015*

**Math**

old area = 400 ft^2 perimeter = 20+80 = 100 so 4 s = 100 s = 25 s^2 = area = 625 625 - 400 = ???
*March 26, 2015*

**Math**

4 = 1 + 3 or 2 + 2 or 3 + 1 so 3 out of 36 which is 1/12
*March 26, 2015*

**Geometry**

L w = 2 2 L * 3 w = 6*2 = 12
*March 26, 2015*

**mathematical physics**

we need the component of force in the direction of motion. F dot vector tangent to motion tangent to motion is velocity vector dX = Vdt if X is position vector and V is velocity vector X = t i + t j + t k V = dX/dt = i + j + k F dot V = y^2z^3 + 2 xyz^3 + 3x y^2 z^2 = t^5 + 2 ...
*March 23, 2015*

**math**

Thank you Reiny. Indeed we had quite a time getting ready for the first day of sailing practice.
*March 23, 2015*

**math - binomial dist, no time to do it**

use binomial distribution. I have to go clean seagull poop and snow off high school sailing floats, will check back this afternoon to see if you got it.
*March 23, 2015*

**Algebra 1**

y = x straight line through origin slope of one. y = 1 x + 0
*March 22, 2015*

**CHEMISTRY**

P V = n R T V same n same R same T same so partial pressure of each is 1/2 atm.
*March 22, 2015*

**Algebra**

http://www.jiskha.com/display.cgi?id=1427052839
*March 22, 2015*

**Algebra**

No problem :)
*March 22, 2015*

**Algebra**

I wrote (3 y - ) (y + ) and tried factors soon saw needed (3 y + ) (y - ) then fooled with 3 and 4 and then 6 and 2 until it worked
*March 22, 2015*

**Algebra**

Sure, fooled around with factors of 12 3 and 4 did not work, 1 and 12 did not work, so tried 6 and 2
*March 22, 2015*

**Algebra**

You are welcome.
*March 22, 2015*

**Algebra**

(3 y + 2)(y - 6)
*March 22, 2015*

**math**

combinations of 15 ten at a time n = 15 r = 10 C(n,r) = n!/[ r!(n-r)! ] = 15! /[ 10! (5!) ] = 15*14*13*12*11 /(5*4*3*2) = 15/15 * 14/2 * 13 * 12/4 * 11 = 7 * 13 * 3 * 11 = 3003
*March 22, 2015*

**algebra**

6 by 6 matrix of possibilities but 5 and 1 is the same as 1 and 5 for example so really not 36 possible results but only the diagonal and those below (or those above) so 6 + 5 + 4 + 3 + 2 + 1 = 21 possible combinations of which 3 add to 6 (they are (3,3)(2,4)(5,1) ) so THREE ...
*March 22, 2015*

**College Math**

new length = 36 - 2x new width = 24 - 2 x so V = (36-2x)(24-2x)x = 864x - 120 x^2 + 4 x^3 I am glad you do derivatives because I do not feel like finding the vertex. dV/dx = 864 -240 x + 12 x^2 0 = 72 - 20 x + x^2 x = [ 20 +/- sqrt(400 -288) ]/2 = [ 20 +/- 10.6 ] /2 = 15.3 or ...
*March 20, 2015*

**physics**

I can not because I do not know how far south the cat walked
*March 17, 2015*

**physics**

mg = 17*9.81 = 167 N weight 70 = mu (167) mu = 70/167 static 53 = mu (167) mu = 53/167 kinetic
*March 17, 2015*

**Algebra**

2 x^2 - 2 x - 2 = -y x^2 - x -1 = -(y/2) x^2 - x = -y/2 + 1 x^2 - x + 1/4 = -y/2 + 1 + 1/4 (x- 1/2)^2 = -(1/2) (y - 5/2) vertex at ( 1/2 , 5/2 ) if x = 6 y = - 2(36) + 12 + 2 = -58 =================== check (5.5)^2 =? -1/2 (-60.5) ??? 30.25 = 30.25 sure enough :)
*March 17, 2015*

**math**

2*60 + 2 w = 200 w + 60 = 100 w = 40
*March 17, 2015*

**Math**

1 % is .01 .02/5 is clearly less than .01 (it is .004) .2/5 is like .4/10 too big 2/5 even bigger 2/50 like 4/100 like .2/5 too big 2/500 is 4/1000 which is small enough (.004 again)
*March 17, 2015*

**math**

3/5 * 1/3 * x = 8 x = 8 * 15 / 3 x = 40 ================ check: 2/5 * 40 = 16 spent, 24 left 2/3 * 24 = 16 spent, 8 left --- sure enough
*March 17, 2015*

**Vectors**

vector QP = 3 i + 8 j + 2 k vector QR = 1 i + 6 j - 2 k cross product i j k 3 8 2 1 6 -2 -28 i + 8 j + 10 k or -14 i + 4 j + 5 k so for plane -14 x + 4 y + 5 z = d try (1,5,6) to get d -14 +20 + 30 = d d = 36 check with (-1,3,2) 14 + 12 + 10 = 36 sure enough we are on a roll ...
*March 17, 2015*

**physics**

(1/2) M V^2 = (1/2) K X^2 1330 v^2 = 4.12*10^6 (.0499)^2
*March 17, 2015*

**Science Help Please**

Your answer to umber 7 is likely to upset any physicist. Please read the chapter in your text. Go back to the chapters on waves on strings and in trumpets. short wave --> high frerquency
*March 13, 2015*

**Science Help Please**

2 A 5 D 6 A 7 D Oh dear :( 13 C
*March 13, 2015*

**physics**

Huh? 500 Joules is 500 Joules.
*March 13, 2015*

**PHYSICS**

20 meters down pressure = rho g h = 1000kg/m^3*9.81*20 = 196,200 = 1.96 *10^5 Pascals I guess the radius is .4 m??? A = pi(.4)^2 F = P*A = 98,621 Newtons
*March 13, 2015*

**vectors and geometry**

2*5 + 3*-2 + 4*1 10 - 6 + 4 8
*March 13, 2015*

**vectors and geometry**

a+b = 6 i -1 j + 0 k trick question or typo cross product = |A||A| sin theta theta = 0 so cross product = 0
*March 13, 2015*

**Check Answers (Math)**

at x = 0, B is below at all other points, B is below so yes, right, B is wider.
*March 10, 2015*