Saturday

May 23, 2015

May 23, 2015

Total # Posts: 31,343

**Fourier Series**

well, you have to break f(x) into two parts for x<0, f(x) = 0 for x >= 0, f(x) = 2x so, a0 = 1/π ∫[0,π] 2x dx = π and for the others just use integration by parts for integrals of x cos(nx), etc.
*April 14, 2015*

**Math**

(12.7*7.5 m^2) * (10.76 ft^2/m^2) * (1 bdl/33ft^2) * ($29.95/bdl) = $930.17 That is the cost for one side of the roof. The cost will actually be a bit higher if only whole bundles can be purchased.
*April 13, 2015*

**Polygons on the coordinate plane**

plural of vertex is vertices. So, draw a rectangle where the length + width = 8.
*April 13, 2015*

**Calculus**

oops.The printed area is 8x12, so the page is 10x15
*April 13, 2015*

**Calculus**

If printed area has height y and width x, then the page size is (x+2) by (y+3) Since xy = 96, the page size s = (x+2)(y+3) = (x+2)(96/x + 3) ds/dx = 3 - 192/x^2 so, ds/dx = (3x^2-192)/x^2 which is zero when x=8 so the page is 10x11 So, how do our calculations differ?
*April 13, 2015*

**calculus**

x^2+y^2 = 225 so, x dx/dt + y dy/dt = 0 Now plug in your numbers and solve for dx/dt
*April 13, 2015*

**Math**

original: v 1st reduction: v^2 2nd: v^4 3rd: v^8 so, v^8 = 27/125 v = (3/5)^(3/8)
*April 13, 2015*

**math 8th grade**

there are 12 face cards P(J,K) = 4/12 * 4/11 P(b,b) = 6/12 * 5/11
*April 13, 2015*

**calculus**

Each square cross-section has width y and height y, so its area is y^2 = 9e^(-2x) So, the volume is the sum of all those squares, or ∫[0,2] 9e^(-2x) dx
*April 13, 2015*

**Math**

The slope of line MN is 0. So, every point has y-coordinate 3. Thus, 2a=3 and P = (3/2,3)
*April 13, 2015*

**Pre-Calc**

they are expressions. You surely know the exact value of cos(30°) as for sin(-3π/5) you would have to construct a pentagon and figure out some side lengths. figure out sin 36° and then sin 72° and then the sine of 108°.
*April 13, 2015*

**Pre-Calc**

1) that would be cos(12°+18°) which I'm sure you know 2) sin(4π/5-7π/5) 3) well, tan/cos = sin/cos^2 and sec = 1/cos
*April 13, 2015*

**Math**

w = 3b
*April 13, 2015*

**What does this mean**

they want between 400 and 500 words. That should fit on two pages.
*April 13, 2015*

**pre - CALCULUS**

well, you know that x=2y-5 so, substitute that into the other equation, solve for y, and then you can get x.
*April 13, 2015*

**MATH**

495,000 501,000 or any other numbers close to 500,000
*April 13, 2015*

**geometry**

40*20*h = 12000 h = 15 so, you want the surface of the bottom and sides of a box 40x20x15 cm.
*April 13, 2015*

**Intermediate Algebra**

There is no solution to #1 since 12 is not less than 0. As written 12 < 12 + 4x < 0 means 12 < 12+4x AND 12+4x < 0 To find such a number, you would need 12 < 0 12 – x > 15 or 7x – 13 > 1 12-x > 15 -3 > x 7x-13 > 1 7x > 14 x > 2 You...
*April 13, 2015*

**Calculus**

If the steel side is x, then xy = 870 and the cost c = 2x+4*2y so, sub in x or y and find dc/dx or dc/dy
*April 13, 2015*

**Algebra 1**

well, when is 4x-8=0?
*April 13, 2015*

**Algebra 1**

What is the excluded value of the rational expression? 2x+6 / 4x-8
*April 13, 2015*

**Pre - CALCULUS**

If you mean x^2/36 + y^2/11 = 1 then you can see that since 36 > 11, the major axis is on the x-axis. So, since b^2+c^2 = a^2, c^2=25, and the foci are at (±5,0)
*April 13, 2015*

**Pre Algebra Probability**

correct
*April 13, 2015*

**pre - CALCULUS**

That's a sigma 4 ∑ (-1)^k (k+11) k=1 = (-12)+(13)+(-14)+(15) = 2
*April 13, 2015*

**Scientific Notation**

1.0*10^-4 -------------- 2.0*10^-9 = 0.5 * 10^5 = 50,000
*April 13, 2015*

**Algebra**

well, just add up the lengths. If the first shelf is x, then x + (2x+18) + (x-12) + (x+4) = 2.5 Now find x, and the 2nd shelf is 2x+18
*April 13, 2015*

**math**

The tip of your little finger is about 1 ml. So, what do you think?
*April 13, 2015*

**Algebra 1**

when the heights are equal, t seconds after B's launch, 220(t-.25)-16(t-.25)^2 = 220t-16t^2 t = 7.0
*April 13, 2015*

**Math**

do you know how many cups in a quart?
*April 13, 2015*

**math**

well, 6 is 96/16, so r = 1/2
*April 13, 2015*

**Algebra 1**

(x+8)^2 - x^2
*April 13, 2015*

**Algebra 1**

thank you
*April 13, 2015*

**Algebra 1**

The size of a computer monitor is given by the length of the diagonal of the screen.The ratio of the height to the width of wide screen monitors is 9:16. Find the expressions for the width and height of a wide screen monitor in terms of the lengthy of its diagonal.
*April 13, 2015*

**Algebra 1**

In a right triangle the adjacent side = 12, the opposite side = 35, and the hypotenuse = 37. What does the opposite angle =? a-71,1 deg b-18.9 deg c-29.2 deg d-90 deg my answer is 18.89 degrees
*April 13, 2015*

**math**

-2h-21+4h <= 9 2h-21 <= 9 2h <= 30 h <= 15
*April 13, 2015*

**Pre-Calculus**

Looks to me like you need -3(x-2)^2 + 13
*April 13, 2015*

**Math???Help**

Assets are + Liabilities are - 235000 -170000 +17900 -5900 -823 +1200 ------------- 77377
*April 13, 2015*

**Math**

what are all those *'s supposed to mean?
*April 13, 2015*

**Algebra 1**

sorry copied answer wrong 27y sqrt 15
*April 13, 2015*

**Algebra 1**

sqrt 15y * 3 sqrt 81y Simplify the radical expression My answer is 27 sqrt 15y^2
*April 13, 2015*

**algebra**

60 burgers and a dozen sodas.
*April 13, 2015*

**math**

dunno. what are the little boxes?
*April 13, 2015*

**algebra**

so, what's the problem? 5.2x-x^2 = 4.8 x^2-5.2x+4.8 = 0 Now just use the quadratic formula to find x. It may be that one of the solutions does not apply, depending on the size of the pipe.
*April 13, 2015*

**math**

clearly, f(a-1) = (a-1)^3-3 That's good as it is, but you might want to expand the binomial power.
*April 13, 2015*

**math**

do you mean (t+1-t^3)^2 or t^2+1-t^3 either way, just replace all the t's with 2's and evaluate the result.
*April 13, 2015*

**algebra,mathematics**

first part already answered I suspect a typo, what with the -x and +x, leaving you with √2 x^2-5=1 √2 x^2 = 6 x^2 = 6 hmmm. not what you expected. How about √(2x^2)-5=1 2x^2=36 x^2=18 Hmmm. Better clean up your notation a bit.
*April 13, 2015*

**maths**

A false B true C true, if you allow complex values. Otherwise, it has no real values at all.
*April 13, 2015*

**math**

as on your other post, use what you have. Since 6y = 3(2y), 5x-3(3x-13)=23
*April 13, 2015*

**math**

well, if you have 5 numbers whose mean is 19, then they must add up to 5*19 = 95 Your sum so far is 58 So, you need two more numbers which add up to 37. Since your median is 19, you need one less than 19 and one greater than 19. So, how about 14 17 19 20 25 You can surely find...
*April 13, 2015*

**math**

r(18c-3d-6+d) I suspect a typo, as that's as far as you can go with what you have. Note that you have 2y=3x-13 So, use that in the other equation to get 5x-(3x-13)=23 Now just solve for x, then get y from that.
*April 13, 2015*

**trigonometry**

A) a = 1/2 r^2θ, so 21 = 1/2 r^2 25π I gotta wonder about an angle of 25π, since 2π is a complete circle... B) 487π = 243(2π) + π C) 1/365 * 2πr
*April 13, 2015*

**PHYSICS math**

If the problem was presented in this language, that's some poor textbook! The distance d (in km) of the plane from you?, me?, them? might be d^2 = 2.1^2 + 1.5^2 + 50^2 In the x-y plane, the angle is arctan(1.5/-2.1)
*April 12, 2015*

**ALGEBRA PLSSSSSS**

Suppose you had x^3-10 = 0 Then the only real zero would be x=∛10, right? Well, this is the same thing. The only real zero is x-12 = ∛10, or x = 12+∛10 The graph is just like the graph of x^3-10, but shifted right by 12.
*April 12, 2015*

**9th grade geometry**

well, that'd just be the sum of the two volumes, right? cone: 1/3 πr^2h = π/3 (6^2)(8) cylinder: πr^2h = π (6^2)(10)
*April 12, 2015*

**calc rates**

draw a cross-section. When the water has depth y, the radius of the surface is r = 3/14 y So, the volume of the water at depth y is v = 1/3 πr^2y = π/3 (3/14 y)^2 y = 3π/196 y^3 dv/dt = 9π/196 y^2 dy/dt If the water is being pumped in at a rate of k cm^3/...
*April 12, 2015*

**calc rates**

dS/dt = 8πr dr/dt dV/dt = 4πr^2 dr/dt so, dV/dt = r/2 dS/dt dS/dt = dV/dt * 2/r The given data thus mean that dS/dt = 500*2/11 cm^2/min
*April 12, 2015*

**Math**

1000/x = tan 40°
*April 12, 2015*

**calc rates**

pv^1.4 = c using the product rule, dp/dt * v^1.4 + 1.4pv^0.4 dv/dt = 0 No wjust plug in your numbers and solve for dv/dt
*April 12, 2015*

**GEOMETRY**

draw a diagram. If you label T = top of lighthouse B = base of lighthouse C = Casey then the angle of elevation is the angle BCT That is, 0° is a horizontal line of sight, meaning that he has to look up at an angle of 58° to see the top of the lighthouse. So, using you...
*April 12, 2015*

**math**

I prefer B, where the order matters.
*April 12, 2015*

**calculus rates**

a = bh/2 da/dt = 1/2 (h db/dt + b dh/dt) Now just plug and chug, solving for db/dt
*April 12, 2015*

**Algebra 2 A Conic Section**

The parabola y^2 = 4px has focus at x=p. You have a parabola y^2+6y = 3x-3 (y+3)^2 = 3(x+2) So, its focus is at (x+2) = 3/4 x = -5/4 and since the line y+3 = 0 is the axis of symmetry, the focus is at (-5/4,-3) as desired.
*April 12, 2015*

**MATH WORD PROBLEM HELP PLEASE**

v = pi r^2 h pi is about 3, so you want r^2 h to be somewhat more than 25 since 24 = 6*2^2, let's try r=2, h=6 pi * 4 * 6 = 75.39 Now you can pick any other set of numbers that multiply similarly to about 25 or more.
*April 12, 2015*

**Algebra 1**

thank you
*April 12, 2015*

**Algebra 1**

Jim shoots an arrow into the air. The height of the arrow in feet, t seconds after shooting, is shown by the function below. h(t)=64t-16t^2 What is the domain of the function and what does it represent?
*April 12, 2015*

**Algebra 1**

h(t)=-16x^2+16t+32 Which statement best describes the term 32?
*April 12, 2015*

**math**

v(t) = df/dt = -32t+160
*April 12, 2015*

**Algebra**

to get started, g(x+h) = 2(x+h)^2 - 3(x+h) = 2x^2 - 3x + 4hx - 3h + 2h^2 for (b) it seems they have a typo. Maybe you can spot it.
*April 12, 2015*

**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*