Friday

August 22, 2014

August 22, 2014

Total # Posts: 17,969

**Analytic Geometry**

sketch it first then find the lengths of the sides for example c^2 = 2^2 + 6^2 = 40 c = 2 sqrt 10 then use law of cosines a^2 = b^2 + c^2 - 2 b c cos A
*August 11, 2014*

**Analytic Geometry**

intersections: x^2 + y^2 - 2x - 2y -2 = 0 x^2 + y^2 + 2x + 2y -2 = 0 ---------------------------subtract -4x -4y = 0 x = - y so along that line of slope -1 now where does x = -y on either circle? 2 y^2 + 2y -2y = 2 y^2 = 1 y = +/- 1 x = -/+ 1 in other words at (-1,1) and (1,-1...
*August 11, 2014*

**Analytic Geometry**

I think you mean "VERTICES" or "corners" in geometry where two straight lines meet.
*August 11, 2014*

**math**

5^3 - 2^3
*August 11, 2014*

**math**

so this time they add to 90
*August 11, 2014*

**math**

supplementary angles add to 180 93 + x = 180 or x = 180 - 93
*August 11, 2014*

**physics**

250 (1000/3600) = 69.4 m/s v = Vi + a t 0 = 69.4 -10t t = 6.94 seconds to stop d = (1/2) a t^2 = (1/2)(10)(6.94^2) = 241 meters
*August 11, 2014*

**statistics gibberish**

Please proof read does body mean boys? what is 60 kg ? who got hired for what? http://davidmlane.com/hyperstat/z_table.html
*August 11, 2014*

**Algebra**

2 v^2 + 4 v - 14 = v^2 + 2 v + 1 v^2 + 2 v - 15 = 0 (v+5)(v-3) = 0 v = 3 or -5 the next one is easy
*August 11, 2014*

**Algebra**

L = 7 + 2 w L w = 99 (7+2w)w = 99 2 w^2 + 7 w - 99 = 0 (2w -11)(w+9) = 0 w = 11/2 L = 7 + 11 = 18
*August 11, 2014*

**chemistry**

By the way molecules of He is the same as atoms of He because there is one atom per molecule. If it had been H2 or O2 there would have been twice as many mols of atoms as mols of molecules.
*August 11, 2014*

**chemistry**

3 times Avagadro's number = 3 * 6.022 * 10^23 = lots of them Hey saying you have a mol of something is the same as saying you have 6*10^23 of them. It is sort of like if you say you have a dozen everyone knows you have twelve.
*August 11, 2014*

**Calculus-Math**

dC/dt = dC/dx dx/dt = 60 dx/dt = 60 [ 3(-1.637) t^2 etc
*August 11, 2014*

**Algebra**

2*3*5* w^4 * v^8 and 2*2*2*3 * y^3 * w^6 *v^2 2*3* w^4 *v^2 or 6 w^4 v^2 is all that is common
*August 11, 2014*

**Algebra**

I just did this about one minute ago. Stop spamming.
*August 11, 2014*

**Geometry**

NO lots of things with 4 straight sides are not rectangles but squares are.
*August 11, 2014*

**Algebra**

You are welcome.
*August 11, 2014*

**Algebra**

w (9-w^2) second factor is difference of squares in general a^2-b^2 = (a-b)(a+b) so w (3-w)(3+w) or -w (w-3)(w+3)
*August 11, 2014*

**physics**

Ah, ha, there was more. initial south momentum = 900 v initial west momentum = 2000 u final south momentum = 2900(16)cos 24 final west momentum = 2900(16)sin 24 so 900 v = 46400 (.9135) and 2000 u = 46400 (.4067)
*August 11, 2014*

**algerbra**

draw a number line from way left to way right +54 - (-17) = 54+17
*August 11, 2014*

**Maths literacy**

base times height. It is the same as a rectangle with a triangle taken off one end and tacked to the other end. Draw it.
*August 11, 2014*

**Maths literacy**

of what ? circle pi r^2 square s^2 rectangle L w general integral of dy dx ?
*August 11, 2014*

**math**

1= integral f(x) dx from 0 to 1 over 1 1= .5 a x^2 + (1/3) b x^3 from 0 to 1 1= .5 a + b/3 and .6 = E(x) = integral x f(x) dx .6 = = integral a x^2 + b x^3 .6 = (1/3) a + (1/4) b solve those two equations for a and b then you can do f(x) from 0 to 1/2 etc
*August 11, 2014*

**Math**

http://davidmlane.com/hyperstat/z_table.html
*August 11, 2014*

**physical science**

Just did, scroll down one question
*August 11, 2014*

**physics**

H2O = 2 + 16 = 18 grams / mol 30/18 = 1.67 mol 1.67 * Avagadro's number 1.67 * 6.022 * 10^23 = 1.004 *10^24 molecules which is quite a few
*August 11, 2014*

**Physics**

I have done several, your turn.
*August 11, 2014*

**PHYSICS**

yes * means "times"
*August 11, 2014*

**PHYSICS**

a = (.90 -0)/2.8 weight = m g = 50 (9.81) friction force = .2 * 50 (9.81) F - .2*50(9.81) = 50 (.9)/2.8
*August 11, 2014*

**physics - so what ?**

What is the question?
*August 11, 2014*

**physics**

50 min = .833 hr t1 = 3/(1.6+v) t2 = 3/(1.6-v) .833 hr = t1 + t2
*August 10, 2014*

**physics**

see this one I just did: http://www.jiskha.com/display.cgi?id=1407726270
*August 10, 2014*

**AP Stats**

By the way the formula used for linear regression is at the bottom of that web page if you need it or are doing the regression by hand. Most scientific hand calculators have an app for linear regression.
*August 10, 2014*

**AP Stats**

I have no idea what you are talking about unless you mean use regression analysis to find a best linear fit to the data. If that is what you are trying to do, Google linear regression for example there is an online calculator here: http://www.alcula.com/calculators/statistics/...
*August 10, 2014*

**maths**

B = J + 2 G = 2 B D = 2 G ---------------- so J = B - 2 G = 2 B D = 2 G = 4 B ------------------ then J + B + G + D = 38 ( B-2 ) + B + 2 B + 4 B = 38 8 B = 40 B = 5
*August 10, 2014*

**physics**

v = Vi + a t 20 = Vi + 9.5 a d = Vi t + (1/2) a t^2 108 = (20-9.5 a) (9.5) + (1/2) a (9.5)^2 solve for a
*August 10, 2014*

**Alegbra**

I do not know present value formula, using head 125/365 = .34247 so t = 8.34247 A = p e^rt 225,500 = p e^.0855 (8.34247) ln 225,500 = ln p + .71328 ln p = 11.6128 p = $110,502.72
*August 10, 2014*

**Math**

c + a = 20 so c = 20-a 12 c + 18 a = 246 12(20-a) + 18 a = 246 240 -12 a + 18 a = 246 etc
*August 10, 2014*

**Physics**

YOU MEAN: xf = xo + vot + (1/2)a t^2 How long does it take the first chestnut to reach the ground? 11 = (1/2) g t^2 t = sqrt (22/9.81) = 1.5 seconds so how long is the second one in the air? t = 1.5 - sqrt(2*2.7/9.81) = 1.5 - .74 = .76 seconds so the second one has to go 11 ...
*August 10, 2014*

**math**

do they have to be different? If not (1 + 1 + 1 + 45)/4 = 12 if they do have to be different (1 + 2 + 3 + 42)/4 = 12
*August 10, 2014*

**math**

Nancy and Sue make 11 bags the first hour all together they make 23 bags per hour they have 149 - 11 = 138 bags to make 138/23 = 6 hours so total of 7 hours 7 * 60 = 420 minutes
*August 10, 2014*

**math typo or nonsens**

Huh, Nancy and Sue make 11 bags per hour, not 12 anyway if they working together make 24 bags/hr then 149 bags / 24 bags/hr = 6.2 hr 6.2 * 60 = 372 minutes
*August 10, 2014*

**Algebra**

(15x+1)(x+2) is correct to check using FOIL First 15 x^2 Outer 30 x Inner 1 x Last 1 * 2 = 2 so 15 x^2 + 31 x + 2 to check using distributive property of multiplication 15 x ( x+2) = 15 x^2 + 30 x +1 (x+2) = x + 2 sum = 15 x^2 + 31 x + 2
*August 10, 2014*

**Algebra**

you turned the sign around in the second line w (9-w^2) w (3-w)(3+w)
*August 10, 2014*

**physics incomplete**

the answer to what you have typed is easy if they were both moving 24 deg west of south at 16 before the collision, they can continue after. However I am sure that is not the case and you have left out some initial conditions.
*August 10, 2014*

**physics**

loss of potential energy = m g (31) = 62 * 9.81 * 31 = 18,855 Joules gain in potential energy of spring = (1/2) k x^2 =.5 * k (31-12)^2 = 180.5 k so k = 18855/180.5 = 104 N/m F = m a force down = m g = 62*9.81 = 608 Newtons force up = kx when x = 31-12 = 19 F up maximum = 104*...
*August 10, 2014*

**physics**

hit at height x ball A drops h-x ball b rises x Ball A (h-x) = h - 4.9 t^2 or x = 4.9 t^2 v = -9.81 t Ball B h = Vi t - 4.9 t^2 v = 9.81 t/2 = 4.9 t so 4.9 t = Vi - 9.81 t or Vi = 14.7 t ------------------ h = 14.7 t^2 - 4.9 t^2 = 9.8 t^2 but x = 4.9 t^2 so I get half way up, ...
*August 10, 2014*

**Algebra**

we know that 81 = 9*9 and that 9+9 = 18 so try (u+9)(u+9)
*August 9, 2014*

**Calculus-Math**

d/dx (x^2y^2 - 2 x) = 2 x y^2 - 2 d/dx (2 x y^2 - 2) = 2 y^2
*August 9, 2014*

**physics**

draw picture get angles in first triangle 180 - 52 = 128 180 -128 - 33 = 19 which is angle opposite the 300 then law of sines sin 19/300 = sin 33/second slope up so second slope = 300 (sin 33 / sin 19) = 502 meters then right triangle sin 52 = h/502 h = 395 meters four ...
*August 9, 2014*

**Calculus-Math**

6 (x^2+y^2)(2x+2ydy/dx)=100(2x-2ydy/dx) find dy/dx at (4,-2) 6(16+4)(8-4dy/dx)=100(8+4dy/dx) solve for dy/dx which is m in y = m x + b then use the given point in the given equation to find b
*August 9, 2014*

**Algebra**

y^3/y^5 = y^-2 x^6 / x^4 = x^2 so y^-2 x^2 or x^2/y^2 or (x/y)2
*August 9, 2014*

**Precal**

r = sqrt (74) theta = tan^-1 (5/7) leave it that way, do not go to degrees 2 r = 2 sqrt(74) draw this axis system to figure out tan theta+pi/2 we are in Quadrant 2 theta degrees from the y axis so now tan of new theta = 7/-5 and we have the point ( 2 sqrt 74 , tan^-1 (-7/5) ...
*August 9, 2014*

**Precalculus**

and no it is the whole ellipse
*August 9, 2014*

**Precalculus**

.... and how did you make out with the spherical coordinates problem Aditya?
*August 9, 2014*

**physics**

First crossing: time to cross = 87/1.5 = 58 seconds so speed of current = 30/58 = .517 m/s second crossing v upstream = 1.5 sin A = .517 sin A = .345 A = 20.2 degrees then if they ask: v across = 1.5 cos A
*August 9, 2014*

**physics**

Yes, I am getting a bit frayed around the edges as well.
*August 9, 2014*

**physics**

(c) v = sqrt (2 g h)
*August 9, 2014*

**physics**

Thrust phase: v = a t v = 17 t v at 20 s = 17 * 20 = 340 m/s (Vi for next phase) h = (1/2) a t^2 = (1/2)(17)(400) = 3,400 m coast up phase: v = Vi - a t v = 0 at top 0 = 340 - 9.81 t t = 34.7 seconds coasting up now 54.7 seconds aloft how high? h = 3,400 + Vi t - 4.9 t^2 h = 3...
*August 9, 2014*

**physics**

It takes her 87/1.5 seconds to cross the current flows 30 meters in 87/1.5 seconds so the current speed is 30 *1.5 /87
*August 9, 2014*

**physics**

This does not make sense. The only thing I can say is that it has a mass of m = 5.10/9.81 = .52 kilograms wherever it is. Is the spaceship in a "zero gravity" orbit around earth? In that case it still has a gravitational force depending on how far from the center of ...
*August 9, 2014*

**physics**

speed across = 7.4 cos 24.8 time = distance/speed = 26.1 / 7.4 cos 24.8 the river speed only says how far downstream he will end up.
*August 9, 2014*

**physics**

moved along three sides of square? say 25 m east, 25/15 s then 25 m north, 25/15 s then 25 m west, 25/15 s so displacement is 25 m north in 75/15 s 25 * 15/75 = 15/3 = 5 m/s north
*August 9, 2014*

**Math**

If Efram is 63 that is 63 - 52 = 11 years later then Cole is 11 + 25 = 36 so it is indeed in 11 years but 11 not 63, is the answer
*August 8, 2014*

**Math**

sure but put it as a new question because we do not always look back
*August 8, 2014*

**Math**

x in the pocket to start then 4 + 2 x then 2 (4 + 2 x ) = 100 8 + 4 x = 100 4 x = 92 x = 23
*August 8, 2014*

**MATH**

multiply both sides by 12 (the least common multiple of 3 and 4) . 9 x = 2 x = 2/.9 = 20/9
*August 8, 2014*

**algebra**

but if you insist on estimating call it 35 / 3 :) which is about 12
*August 8, 2014*

**algebra**

it is so fast to say 7 1/5 is 36/5 that I call estimating here going kind of out of my way :)
*August 8, 2014*

**algebra**

36/5 / 3/5 = 36/3 = 12
*August 8, 2014*

**Algebra**

2.5 * 60 = 150 minutes 30 + .05*150 = 30 + 7.5 = $ 37.50
*August 8, 2014*

**algebra**

lol just did 36/5 / 3/5 = 12
*August 8, 2014*

**By the way**

Other than that - Good job !
*August 8, 2014*

**Precalculus**

http://mathworld.wolfram.com/SphericalCoordinates.html
*August 8, 2014*

**Precalculus**

are you sure z is not r cos phi in math theta is usually i the xy plane x = r sin phi cos theta y = r sin phi sin theta z = r cos phi In engineering and physics these conventions are often different, nut I suspect you should be using phi as the angle down from the z axis, not ...
*August 8, 2014*

**math**

9 x were boys 8 x were girls 17 x total originally 4 x girls left so then there were 9 x boys 4 x girls 13 x total 9 x - 15 = 4 x 5 x = 15 x = 3 I guess you can do 17 x and 4 x
*August 8, 2014*

**Algebra**

I started with Calculus first as well, but changed my mind after drawing the picture.
*August 8, 2014*

**Algebra**

angle from x axis to tangent = 45 + sin^-1 ( sqrt 6/3sqrt2) = 45 + 35.3 = 80.26 deg x = 2 sqrt 3 * cos 80.26 y = 2 sqrt 3 * sin 80.26 y/x = tan 80.26 = 5.82
*August 8, 2014*

**Algebra**

whoops, sorry h^2 = 18 - 6 = 12 h = 2 sqrt 3
*August 8, 2014*

**Algebra**

draw circle, center at (3,3) radius sqrt 6 draw line (hypotenuse it turns out) from (0,0) to (3,3), length is 3 sqrt 2 draw our tangent, hits circle at 90 degree angle to radius to that point, length is h so h^2 = 18 + 6 = 24 h = 2 sqrt 6 I think you can figure out the ...
*August 8, 2014*

**Algebra**

where does the tangent to the circle from the origin hit the circle?
*August 8, 2014*

**Ethics**

The first one is just accusatory, which just elicits a defensive response. The second one requires that the wrong doers be religious. We can not count on that. Who knows where intuition will lead? So I suppose I will have to agree with you.
*August 8, 2014*

**math**

aaarrrggghhhh, feet and inches and stuff :( anyway if g = -32 ft/s^2 then I will have to admit that the distance fallen from a still start is s = 16 t^2 (not r^2 by the way, falls straight down, not in a circle) s = 16 (64) = 1024 answer B which we did not need a calculator ...
*August 8, 2014*

**math**

well, if one were a prime number then 1986 would do BUT since it is not (any number greater than one not divisible by anything but ---), then 1987 would do since surely 2 is a prime number.
*August 8, 2014*

**maths**

x^2 = (c-b)/a ? x = sqrt [(c-b)/a] well, (c-b)/a better be positive and a square of some integer (which makes it positive anyway) for example if (c-b)/a = 5 then x = sqrt 5 which is hard to express as a ratio of integers and if (c-b)/a is -4 then we have 2 i and i, the square ...
*August 8, 2014*

**Math (fibonacci**

It would help if that last date were odd :)
*August 8, 2014*

**Math (fibonacci**

By the way I suspect you mean 2000 not 200
*August 8, 2014*

**Math (fibonacci**

y = 1985 + x 200 = x + y so 200 = x + (1985+x) back to you :)
*August 8, 2014*

**Physics**

yes, good to remember v = -sqrt (2 g h) here v = -sqrt (2*9.81*.75) = -3.84 m/s 1.7 = sqrt (2 *9.81 * h) h = .1472986748 I think g is 9.81, you use 9.8 some classes use 10
*August 8, 2014*

**science**

I think I know what you mean. If you calculated the time until the ball reached maximum height and called that time t, then the total time in the air is 2t by symmetry
*August 8, 2014*

**science**

yes they both start with Vi = 0 and accelerate downward at 9.81 m/s^2
*August 8, 2014*

**Physics**

You are welcome.
*August 8, 2014*

**Physics**

yes, 0 = 42 + 75 a a = - .56 d = Vi t + .5 a t^2 d = 42(75) - .28(75)^2 = 3150 - 1575 = 1575
*August 8, 2014*

**History**

I do not see a problem in using the same things as answers an earlier question. You have me pretty confused though about what you think are advantages and disadvantages of ethnic neighborhoods. What do you think are advantages and what do you think are drawbacks?
*August 7, 2014*

**History**

cultural diversity and learning new cultures would not particularly be an advantage of an ethnic neighborhood. A family that moved into a mixed neighborhood would probably learn the new language and traditions faster. I would say advantages include mutual support both in ...
*August 7, 2014*

**what is the question ?**

You want zeros of y or what? if zeros: 4 x^2 - 12 x + 9 = 0 (2 x-3)(2x-3) = 0 x = 1.5, 1.5 double root If vertex etc: 4 x^2 -12 x = y - 9 x^2 - 3 y = (1/4)(y-9) x^2 - 3 y + 9/4 = (1/4)y (x-1.5)^2 = y/4 vertex at (1.5 , 0) which we knew already
*August 7, 2014*

**physics**

Well, there is a hard way and an easy way. Easy way height = h angle = A with no friction KE gained in slide = m g h (1/2) m v^2 = m g h v = sqrt (2 g h) average speed = v/2 = .5 sqrt (2 g h) time = average speed * h/sin A t = .5 h sqrt (2 g h) /sin A now with work done ...
*August 7, 2014*

**math**

12.5= 3/k multiply both sides by k 12.5 k = 3 divide both sides by 12.5 k = 3 / 12.5
*August 7, 2014*

**physics whoops**

Whoops, sorry, Steve is right.
*August 7, 2014*

**physics**

since the total displacement vector is zero the average speed is zero. let i be unit vector from point A to point B velocity outbound = 40 i velocity back = -60 i (40 - 60)/2 = -10
*August 7, 2014*

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