Friday

July 3, 2015

July 3, 2015

Total # Posts: 32,079

**ALGEBRA**

It might be easier to get rid of the fraction. Just multiply through by 2 and you have x^2 - 2x + 10 = 0 Now just apply the quadratic formula.
*April 12, 2015*

**Math help!**

let u = x/(1-x). Then you have u^2-u-6=0 (u-3)(u+2) = 0 So, you have x/(1-x) = 3 x = 3-3x x = 3/4 or x/(1-x) = -2 x = -2+2x x = 2
*April 12, 2015*

**Math Word Problem**

so, where do you get stuck? Hint: 4 * ab/2 = 2ab
*April 12, 2015*

**Math**

recall that the line with slope m through (h,k) is y-k = m(x-h) which you can rearrange into slope-intercept form. For the circle, try rewriting that as x^2-2x + y^2+5y = -5 Now complete the squares x^2-2x+1 + y^2+5y+25/4 = -5 + 1 + 25/4 (x-1)^2 + (y+5/2)^2 = 9/4
*April 12, 2015*

**Algebra**

s = rθ, where θ is in radians so, 4*100*pi/180
*April 11, 2015*

**Math**

wrong. it is not a function if the same x-value is related to more than one y-value. Draw any graph. If a vertical line intersects the curve in more than one place, it is not a function.
*April 11, 2015*

**Math**

4.5/1.1 * 10^1 looks like about 40
*April 11, 2015*

**physics**

this should help http://farside.ph.utexas.edu/teaching/302l/lectures/node137.html
*April 11, 2015*

**calculus**

just to be precise, h = 1/(pi r^2)
*April 11, 2015*

**calculus**

no ideas at all v = pi r^2 h so, h = (1/pi r^2) to find max volume, dv/dt = 2pi r h now plug in the value for h, and solve for dv/dr = 0
*April 11, 2015*

**Math**

better start reviewing the trig functions. 10/x = sin 55
*April 11, 2015*

**Math**

tan x = 1.5/8.0
*April 11, 2015*

**Math**

check the related questions below
*April 11, 2015*

**algebra**

x^4y - y^5 y(x^4-y^4) y(x^2-y^2)(x^2+y^2 y(x-y)(x+y)(x^2+y^2)
*April 11, 2015*

**algebra**

Hmmm. (2d-f)/3 = (f-3d)/5 5(2d-f) = 3(f-3d) 10d - 5f = 3f - 9d -8f = -19d f = 19/8 d
*April 11, 2015*

**math**

this is similar to the one you posted with volumes. What do you think?
*April 11, 2015*

**algebra**

x*5 <= 8
*April 11, 2015*

**math**

see the related questions below
*April 10, 2015*

**algebra**

2|x + 1/3| < 9 |x + 1/3| < 9/2 -9/2 < x + 1/3 < 9/2 -29/6 < x < 25/6 See http://www.wolframalpha.com/input/?i=2%7Cx+%2B+1%2F3%7C+%3C+9
*April 10, 2015*

**Calculus(easy)**

f' is the slope of f if f' > 0, then the curve is sloping upward That is, f is increasing So, we need to find where f' > 0 Since (x−3)^4(x+18)^8 is always positive (even powers are never negative) except at x=3 or x=-18 then f' > 0 where (x-5) &...
*April 10, 2015*

**math**

since 1/2 is 2(1/4), multiply the top by 2o to get 10/3 x + 1/2 y = 20 Then 1/2 y = 20 - 10/3 x Plug that into the 2nd equation and you have 1/3 x + (20 - 10/3 x) = 5
*April 10, 2015*

**algebra**

yes, I can solve it. what did you do to get your answer? I get x = 6 or -4
*April 10, 2015*

**algebra**

if the numbers are x,x+1,x+2 then we want x^2 + (x+1)^2 = (x+2)+2 what do you get?
*April 10, 2015*

**algebra**

rationals reals
*April 10, 2015*

**geometry**

So, did you use congruent corresponding parts AE and CE to show right triangle AED congruent CED ?
*April 10, 2015*

**geometry**

I'm sure you can find several versions of this via google.
*April 10, 2015*

**math**

the distance z is given by z^2 = 120^2 + 130^2 + 10^2
*April 10, 2015*

**Math**

(b) (c) and (f) are all true The question is poorly worded.
*April 10, 2015*

**pre - CALCULUS**

so, what is the leading coefficient test? f(x) = x^2 (x+2) if f(x)=0, then you must have either x^2 = 0 or (x+2) = 0 Note that x^2 is always positive. SO, at x=0, the graph touches the x-axis from above, then goes up again at x = -2, f(x) changes sign from - to +, so the graph...
*April 10, 2015*

**Math**

P(x) = -x^2+600x-3000 x(t) = 1.5t^2-2t dP/dt = dP/dx * dx/dt = (-2x+600)(3t-2) = (-2(1.5t^2-2t))(3t-2) = -9t^3+18t^2-8t = -2261 or, dP/dt = (-2x+600)(3t-2) = (-119)(19) = -2261
*April 10, 2015*

**pre - CALCULUS**

Assuming you mean h(x) = (6x-14)^8 then just make f(x) =x^8 g(x) = 6x-14 that way (f∘g)(x) = f(g(x)) = (g(x))^8 = (6x-14)^8
*April 10, 2015*

**Pre - CALCULUS**

you are correct about x = (12+√24)/12 There is also x = (12-√24)/12
*April 10, 2015*

**Pre - CALCULUS**

ever hear of the quadratic formula? x = (-12±√(144-120))/(2*6)
*April 10, 2015*

**Pre - CALCULUS**

by precalc you should surely know how to find the roots of a quadratic. What did you get?
*April 10, 2015*

**Calculus**

as usual, begin by drawing a diagram. Clearly, the distance z is the hypotenuse of a triangle with sides 2 and 6. Now, at time t hours from when the car passed the intersection, the distance z is z^2 = (55t)^2 + 6^2 so, when the car is 2 miles past the intersection, t=2/55, ...
*April 10, 2015*

**algebra--1 question**

max height at the vertex, which is at t = 23/4 You should certainly not think that the max height is 11.6, since it started off at 20.
*April 10, 2015*

**algebra 1**

could you be a bit more vague?
*April 10, 2015*

**Math**

so, the area is two trapezoids and four rectangles 2[(8+14)/2 * 18] + 8*11 + 14*11 + 18*11 + 11√(6^2+18^2)
*April 10, 2015*

**physics**

total angular momentum must be constant.
*April 10, 2015*

**Math**

you should know that the sides of a 30-60-90 triangle are in the ratio 1:√3:2 so, the triangle formed by your ladder has sides 3:3√2:6
*April 10, 2015*

**Math**

well, 45 = 3*15 = 3*(3 * 5) 60 = 3*20 = 3*(2^2 5) 180 = 2^2 3^2 5 So, the third number is 3*(3 * 2^2 * 5) = 180
*April 10, 2015*

**Mathematics**

since the ratio is constant, 50/2.25 = x/18
*April 10, 2015*

**geometry**

(a) reflected in y=0 and stretched vertically by 10 (b) shifted left 3 and up 3
*April 10, 2015*

**ANSWER ASAP!!!!!!! PHYSICS**

well, the vertical speed is 9.8t so the probe cannot fall for more than 60/9.8 = 6.12 seconds. That means the plane cannot be higher than 183.67 m high. so, at h meters altitude, with horizontal velocity v, the probe will land with speed s = √(v^2+4h^2) The probe will ...
*April 10, 2015*

**Math**

well, 355 = 1812 but I don't think that is what is wanted.
*April 10, 2015*

**Calculus**

well, you have the formula v = 4/3 pi r^3 dv/dt = 4pi r^2 dr/dt Now just find r from v, and you know that dv/dt = -2, so solve for dr/dt
*April 10, 2015*

**Math**

you are correct.
*April 9, 2015*

**pre - CALCULUS**

better write your function. I can't decipher it. How about f(v) = jlkjasklj if 0 <= v < 1.79 ahahhahas if 1.79 <= v < 20 and so on, each section on its own line. And you can lose those 𝑡 characters, which show up as small boxes on my browser.
*April 9, 2015*

**Mathw(URGENT pls)**

use induction. Let the sum be f(n) for k=1, it is clear that 1/(1*2*3) = 1(4)/(4*6) Now assume true for k=n and see what happens for k=n+1 1/(1*2*3) + ... + (2n-1)/(n(n+1)(n+2)) + (2(n+1)-1)/((n+1)(n+2)(n+3)) = n(3n+1)/(4(n+1)(n+2)) + (2n+1)/(n+1)(n+2)(n+3) = n(3n+1)(n+3) + 4(...
*April 9, 2015*

**Mathw(URGENT pls)**

I get n(3n+1) --------------- 4(n^2+3n+2) How did you do it?
*April 9, 2015*

**Calculus**

y = 1/(1+be^kt) y' = kbe^kt/(1+be^kt)^2 y' will be greatest when y" = 0 y" = k^2be^kt(3e^kt-1)/(1+be^kt)^3 so, that will be when t = -1/k ln3 In this case, when t = 1.48
*April 9, 2015*

**Earth Science**

thank you
*April 9, 2015*

**Earth Science**

Which of the following are you most likely to experience a-total solar eclipse b-total lunar eclipse c-full moon d-partial lunar eclipse? my answer is full moon
*April 9, 2015*

**Math**

A is what you want B is just y = 8x C is y = (12-4)x D is y = 12x - 12*4 = 12(x-4)
*April 9, 2015*

**Calculus**

f(x) = √(2x) g(x) = f^-1(x) = x^2/2 f'(x) = 1/√(2x) g'(x) = x So, we want 1/√(2c) = c 1/2c = c^2 1/2 = c^3 c = (1/2)^(1/3)
*April 9, 2015*

**Calc AB**

clearly, since f'(-3) = 0, f^-1 has a vertical tangent at x = f^-1(-3) = 2.
*April 9, 2015*

**Calc AB**

Looks like D to me
*April 9, 2015*

**Calc AB**

Hint: dx/dy = 1/(dy/dx)
*April 9, 2015*

**Calculus AB**

well, f^-1(x) = 9-x^2, so ...
*April 9, 2015*

**Chem**

Volume of nitrogen gas is 125ml atmospheric pressure is 763mm Hg the water temperature inside the eudiometer is the same as the level of the water in the beaker. Calculate the volume if the nitrogen at STP. P1V1/T1=P2V2/T2
*April 9, 2015*

**Calc**

that is just the integral of 3x^-6 - 4|x| just use your power rule.
*April 9, 2015*

**Integral**

just use the power rule on u^(-5/4) + 5.5 u^(1/2) du
*April 9, 2015*

**Calculus**

y=2x xyz=k, so z=k/2x^2 the cost c is c(x,y,z) = 6xy + 10(2xz + 2yz) c(x) = 6x(2x) + 20(3x)(k/2x^2) = 12x^2 + 30k/x
*April 9, 2015*

**math (explanation and answer)**

The circumference of the original paper is 2πR If the arc AB subtends an angle θ, then the circumference of the cone formed is 2πR - Rθ = R(2π-θ) So, the radius of the cone is r = R(1-θ/2π) Since the slant height of the cone is still r, ...
*April 9, 2015*

**math**

y=3
*April 9, 2015*

**calculus (please with steps and explanations)**

This was done by Damon, but here's my take ∫[0,5](f(x)+2) dx = ∫[0,5] f(x) dx + ∫[0,5] 2 dx = 4 + 2x[0,5] = 4 + 10 = 14 Since we are dealing with an even function, ∫[-5,5] f(x) dx = 2∫[0,5] f(x) dx = 2*4 = 8
*April 9, 2015*

**Calculus**

I can't see the diagram, but it appears that if the shadow is x, then 25/x = tanθ so, -25/x^2 dx/dt = sec^2θ dθ/dt -25/2500 dx/dt = (1+1/4)(-1/4 * π/180) Now just solve for dx/dt
*April 9, 2015*

**Algebra 1**

well, since they are usually written as y = a * b^x it seems pretty clear, wouldn't you say?
*April 8, 2015*

**physics**

If the first object takes t seconds to hit, h - 4.9t^2 = 0 t = √(h/4.9) the second object is thus h-4.9(t-1)^2 = 20 h = 31.63 m
*April 8, 2015*

**Math**

Thomas put 1/4 of the c coins he had in his pocket into the jar under his bed. He put 16 coins into the jar. The equation that models this situation is 1/4c = 16. How many coins did Thomas have in his pocket? a 4 coins b 12 coins c 20 coins d 64 coins The answer would be c.
*April 8, 2015*

**AP CALC**

since x^2+y^2+z^2 = 4 using symmetry, we can take 8 times the volume in the first octant. Then v = 8∫[0,2] ∫[0,√(4-x^2)] ∫[0,√(4-x^2-y^2)] dz dy dx
*April 8, 2015*

**Math**

no. rays might be parallel such an angle of zero measure could be said to fit the constraints, but that might not be allowed.
*April 8, 2015*

**calculus**

assuming an open box, then x^2 + 4xz = 426 v = x^2 z = x^2 (426-x^2)/4x = 426x - x^3
*April 8, 2015*

**Math didn't post problem right**

find the Quotient: 1,754/21 a 1733 b 21 11/83 c 83 11/21 d 1775 Is C the correct answer. I had post the problem wrong. Sorry
*April 8, 2015*

**Math**

find the quotient: 1,754/12 a 1733 b 21 11/83 c 83 11/21 d 1775 Would C be the correct answer?
*April 8, 2015*

**Math**

I agree.
*April 8, 2015*

**Math**

The determinant |2 6| |1 3| = 6-6 = 0 So, there is no inverse
*April 8, 2015*

**Algebra**

Better think again, S. the line x=4 is a vertical line The vertical line through (-6,-2) is x = -6
*April 8, 2015*

**Algebra 2 math**

the triangle's 3rd side is √(41^2-40^2) = 9 So, now you know all three sides, and the angles, so the trig functions are easy to read off. sin G = 9/41 and so on
*April 8, 2015*

**linear algebra-urgent**

you know p. Can you not figure its length? √(33^2+44^2) = 55
*April 8, 2015*

**linear algebra-urgent**

#1 a unit vector in the direction of w is z=[3/5;4/5] p = u.z = 11/5 z = [33/25;44/25] = [1.32;1.76] you are correct |kp| = k|p| = 55/25 k So, k = 25/55 As for the span, that is usually defined for a set of vectors. span{w} would just be w. So, any vector orthogonal to w will ...
*April 8, 2015*

**math**

54.2/16 * 2.31
*April 8, 2015*

**math**

Not even close. The area is length * width, or 8(6x+3) = 48x+24 6x+3 is not 9x. Even if it were, 9x+8 would be half of the perimeter, not the area.
*April 8, 2015*

**Geometry**

wrong. The two circular ends of the cylinder are usually parallel. I guess that leaves only one other possibility, right?
*April 8, 2015*

**math**

well, just start listing them: 3568 3586 ... 8653 There are only 24 of them.
*April 8, 2015*

**Algebra**

If Nathan is x and Nicole is y, we have y = 2/3 x (y-2) = 1/2 (x+5) Now just solve for x.
*April 8, 2015*

**Math (Please help ASAP)**

It's just a quadratic in p: q+p^2-33p = 9 p^2 - 33p + (q-9) = 0 Now just use the quadratic formula to get the two values for p.
*April 8, 2015*

**Math**

1/3 (9x-2) + 1 = 2(4x+1) You can multiply by 3 to get 9x-2 + 3 = 6(4x+1) 9x+1 = 24x+6 -5 = 15x x = -1/3
*April 8, 2015*

**chemistry**

CuS + 2HNO3 = Cu(NO3)2 + H2S That should help, right?
*April 8, 2015*

**trigonometry**

speed = distance/time, so 2π*3960mi/24hr = ? mi/hr 2πrad/24hr = ? rad/hr
*April 8, 2015*

**trigonometry**

v = 2π*14in/rev * (.5/2π)rev/s = 28 in/s .5rad/s * 1rev/2πrad * 60s/min = 4.77 rev/min .5rad/s * 180°/πrad = 90/π °/s
*April 8, 2015*

**maths**

this is just an A.P. with d = 4 a = 100-20*4 = 20 So, the sum of 21 rows is S = 21/2 (20+100)
*April 8, 2015*

**math**

draw your triangle the other side is √15 since we are in QII and sin is positive, x = -√15 y = 1 r = 4 so, cosx = -√15/4 Now use those values to plug into your half-angle formulas.
*April 8, 2015*

**Pre-calc**

Or, you can go the other way sin(7x) = sin(6x)cos(x) + cos(6x)sin(x) and start expanding those as well, till all you have left is a bunch of sin(kx).
*April 7, 2015*

**Pre-calc**

http://www.wolframalpha.com/input/?i=%28sinx%29%5E7 will show the answer you need. sin^7 = sin(1-cos^2)^3 Now you can start expanding and using the sum formulas. I'm sure a google search will show up all the gory details.
*April 7, 2015*

**math**

why use } when / is available? (4/9)(1/8) = 1/18 (1/18)(1/3) = 1/54
*April 7, 2015*

**Math**

correct.
*April 7, 2015*

**Math**

There is clearly a typo in the above, since the function is a parabola which opens upward, and so has no maximum. If we go with y = -6x^2+42x-60 then that works out to y = -6(x^2-7x+10) = -6(x-5)(x-2) The vertex is at x = 3.5, so that means 3500 boards. You know, if you keep ...
*April 7, 2015*

**Math**

-5x^2 - 30.5x = -1/10 (50x^2 - 305x) = -5/10 x (10x-61) I suspect a typo, since the roots of the above are clearly 0 and 6.1
*April 7, 2015*

**Math**

no, it can be any real number.
*April 7, 2015*