Tuesday

November 24, 2015
Total # Posts: 35,768

**Physics [Help, need answer in 10 min]**

Never come here expecting instant help. Someone who can do it may not be available just now. Still, this problem seems pretty straightforward: F = GMm/r^2 = 6.673*10^-11 * 1.99*10^30 * 7.36*10^22 ------------------------------------------- (1.496*10^11 + 3.84*10^8)^2 = 4.345*...
*November 19, 2015*

**physics**

Just use the formula for each point and add 'em up. They're all in a nice straight line, so there are no vector calculations involved. Take a peek at http://hyperphysics.phy-astr.gsu.edu/hbase/electric/potpoi.html
*November 19, 2015*

**physics**

midway between the charges, of course.
*November 19, 2015*

**Math: Geometry**

huh? An easy isosceles trapezoid? Mark off P and Q on AB so you have a rectangle PQCD. That means that AP=QB=(9-8)/2 = 1/2 Now the height h of the trapezoid is h^2 = 7^2 - (1/2)^2 And the area is h(8+9)/2
*November 19, 2015*

**Math**

Just looking at the factors will not work, because you can't see the translations. Expanding and then completing the square, (x+3)(x-1) = x^2+2x-3 = (x^2+2x+1)-4 = (x+1)^2 - 4 So, that's x^2, translated left 1 and down 4 Or, using symmetry, you know the axis of ...
*November 19, 2015*

**Algebra 2**

As I read it, the directions were to list the possible rational zeros, not to actually find them. Looks to me like Truda did it just right.
*November 19, 2015*

**function rule**

a(w) = w(w+4)
*November 19, 2015*

**algebra**

common denominator is 60, so 15x-12x-20=64 3x=84 x=28
*November 19, 2015*

**Algebra 2 (Math)**

well, geez - start substituting! y=z+1 x=-3z+6, so (-3z+6)+2(z+1)+z=14 Now just solve for z, then you can get x and y.
*November 19, 2015*

**Calc**

f(t) = 800(1/2)^(t/5700) You can see that every time t increases by 5700, you have another power of 1/2, or a half-life. So, using that, just plug in your values for t. You can get an estimate by noting that 11400 = 2*5700 45000 ≈ 8*5700
*November 19, 2015*

**Math**

a scale factor of 3 means that all distances are multiplied by 3. So, multiply all your coordinates by 3.
*November 19, 2015*

**math**

assuming you mean (4x^3-x)/((2x+1)(6x-3)) = (x(2x-1)(2x+1))/(3(2x+1)(2x-1)) = x/3 = 3333 well, 7 men for 7 hrs for 1 day = 1 work unit 7 men for 1 hr for 1 day = 1/7 wu 1 man for 1 hour for 1 day = 1/49 wu 5men * 5hrs * 5days = 125/49 wu or, just do the ratios in-line (5/7)(5/...
*November 19, 2015*

**math**

At interest rate x, 2100(1+2x) = 2352 x = (2352/2100 - 1)/2 = .06 = 6% so, x-1 = 5% My age=m grandfather is g (g-16) = 9(m-16) (g+8) = 3(m+8) so, solve for m and g, and you want (m-8)/(g-8) = ?
*November 19, 2015*

**Algebra**

.06p = 7500 Now using that p, find .07p Or, just calculate (7/6)(7500)
*November 19, 2015*

**Algebra 2**

take a look at http://www.zweigmedia.com/RealWorld/LPGrapher/lpg.html Enter your problem. It will find a solution and even provide a graph. Be sure to set the x- and y-ranges appropriately. You can get an example to show the syntax. For this problem, just copy/paste minimize c...
*November 19, 2015*

**Algebra 2**

y = z+1 and x = -3z+6, so (-3z+6)+2(z+1) + z = 14 so, find z, then x and y
*November 19, 2015*

**algebra 2a help**

correct you have trouble with the word "minimum"?
*November 19, 2015*

**algebra 2a help**

true It's clear you need to review your introduction to complex numbers.
*November 19, 2015*

**Algebra**

clueless? check the topic of this section of your text. Review the definition of tan(x). Draw a diagram. Then it is clear that the height is given by 1.5 + 4.2 tan 74°
*November 19, 2015*

**Math**

maybe
*November 19, 2015*

**Calculus**

well, of course A,B,C depend on their denominators. But if you list them in the same order after solving for the values, the result should be (44/9)/x - (44/9)/(x+3) - (44/3)/(x+3)^2
*November 19, 2015*

**Pre-Calc**

No, but there are only a few points. Describe the picture. If a and b are on the same side of the vertical line down from the tower, then a-b=9°. If not, a+b=115° Where does the 43° angle come into play?
*November 19, 2015*

**Calculus**

forgotten your Algebra I? x/(6x-5) = 1/6 + 5/6 * 1/(6x-5)
*November 19, 2015*

**math**

AB => x+5 = y BA => 11-y = x So, just solve for x and y.
*November 19, 2015*

**math**

If the amounts in A and B are x and y, then .10x + .15y = 4000 .10(1.2x) + .15(1.1y) = 4000+500
*November 19, 2015*

**algebra**

since a=πr^2 = 78.5 = 25π, r=5 since s=rθ = 6π, θ = 6π/5 = 216°
*November 19, 2015*

**Calculus 1**

by l'Hospital, (a) -> (1/x + 2)/(2x) -> 3/2 (b) -> 2x/e^x -> 2/e^x -> 0
*November 19, 2015*

**Algebra I**

all correct. good work
*November 19, 2015*

**Maths**

xy=800, so x == 800/y x+2y = 800/y+2y for minimum value, you need -800/y^2 + 2 = 0 y=20 This is just like the fencing problems where minimum fencing for 3 sides of a rectangle is desired. The amount is evenly divided between the x's and the y's
*November 19, 2015*

**math**

sounds like the response to a question on Jeopardy! Want to revise the syntax?
*November 19, 2015*

**math**

that would be correct, since then the sin curve is above the cos curve.
*November 19, 2015*

**math**

To get the algebraic (signed) area, just do ∫[-π/2,π/2] cos(t)-sin(t) dt = 2 But that value subtracts the area where cos < sin. If you want the physical area, you need to break up the region at π/4. http://www.wolframalpha.com/input/?i=%E2%88%AB[-%CF%80...
*November 19, 2015*

**math**

cost: 40 desired revenue: 40*1.10 = 44 now divide that by the 80 good bananas to get the price for each banana.
*November 18, 2015*

**math**

cost: (120 * 1/6) + (120 * 1/5) = 44 sales: (120+120)/4 = 60 profit: 60-44=16 % profit = 60/44 = 15/11 15/11 - 1 = 4/11 = .3636 = 36 4/11 % It makes it harder to arrive at the solution when you have typos in the problem...
*November 18, 2015*

**Math**

clearly, the extra 4 balls added 760 g now do the math.
*November 18, 2015*

**Math**

p=3q q = r-1.1 r = p-1.3 q = p-1.3-1.1 q = 3q-2.4 ...
*November 18, 2015*

**Identities**

cos2x/sin2x + sinx/cosx cos2x/sin2x + 2sin^2 x/(2sinx cosx) (cos2x + 2sin^2 x)/sin2x (1-2sin^2 x + 2sin^2 x)/sin2x 1/sin2x csc2x
*November 18, 2015*

**Mathematics**

this is explained here: http://socratic.org/questions/how-do-you-use-limit-to-prove-the-derivative-of-secx-secxtanx google is your friend. Use it.
*November 18, 2015*

**trigonometry**

parent is clearly sin(θ) -34sin(10θ+10π) = -34sin(10(θ+π)) period is 2π/10 phase shift is -π amplitude is 34 vertical shift is -14 midline is y = -14 see the graph at
*November 18, 2015*

**Pure Mathematics**

one way is Gaussian elimination, as shown here: http://www.gregthatcher.com/Mathematics/GaussJordan.aspx Just enter your matrix of coefficients
*November 18, 2015*

**Calculus III**

The integral is easy enough, but I sure don't see where symmetry helps, especially in that region R.
*November 18, 2015*

**Mathematics**

nope. it cannot. Lose the 5
*November 18, 2015*

**Math**

Come on... 9.50 - 7.18 = 2.32
*November 18, 2015*

**Math**

well, did you actually do the subtraction? 50-18 ≠ 48
*November 18, 2015*

**Math**

ahem - you multiply by 100 to turn a number to a percentage: 1 = 100% 10 = 1000% 503,000,000 = 5.03x10^8 5.03x10^8 = 5.03x10^10 % But that's a different problem, eh?
*November 18, 2015*

**Math**

1.331
*November 18, 2015*

**Math**

The 15th term comes after 14 multiplications. So, 4n^14
*November 18, 2015*

**Mathematics**

tan2x = sin2x sin2x/cos2x = sin2x sin2x(cos2x-1) = 0 so, sin2x=0 or cos2x=1 That help?
*November 18, 2015*

**Math**

tanθ = sinθ sinθ/cosθ = sinθ sinθ = sinθ cosθ sinθ - sinθ cosθ = 0 sinθ(1-cosθ) = 0 No idea where the 5 came from.
*November 18, 2015*

**Algebra 1- Just one question**

4 shirts = 1 pants 8 shirts = 2 pants so, 2*18.98 = ?
*November 18, 2015*

**Math**

if 25f = 100 f = 25f/25 = 100/25 = 4 If I told you 2*f=10, would you have trouble finding f? Probably not. So, when confronted with uncomfortable numbers, try solving the same problem with easy numbers, and then follow the same steps.
*November 18, 2015*

**Pre Calculus 1**

the decay function after t years is 0.3^(t/4) You want the half-life, or 0.5^(t/k) 0.5^(t/k) = 0.3^(t/4) t/k log 0.5 = t/4 log 0.3 k = 4log.5/log.3 = 2.3 so, you have (1/2)^(t/2.3) and thus the half-life is 2.3 years for the other, the population is 40*1.03^t
*November 18, 2015*

**Math Asap**

no, it would be an integer :-)
*November 18, 2015*

**Math Asap**

sorry; √9 is a rational number. In fact, it is 3, an integer. Most of the time, a √ is irrational, but not always.
*November 18, 2015*

**Math**

the -ir prefix means "not"
*November 18, 2015*

**math**

2(x+y) = 3(x-y)+8 (x+y)/2 = (x-y)+1 The numbers are 7 and 3
*November 18, 2015*

**math**

(a) clearly, 20 * -2 (b) 10*4 - 8*2 + 2*0 (c) 4*c - 5*2 = 14 (d) 20-(c+5) using the value for c above
*November 18, 2015*

**Analytic Geometry**

Line Q has slope -1/5; so do all parallel lines Perpendicular lines P therefore have slope 5 So, just use the point-slope form of a line to write the needed equations. Now, what is the slope of a line 45° clockwise from P? If P makes an angle Ø with the x-axis, then...
*November 18, 2015*

**math**

If you mean r(t) = 3+t^2, then dr/dt = 2t If you really mean rt = 3+t^2, then r = 3/t + t dr/dt = -3/t^2 + 1
*November 18, 2015*

**Algebra II**

clearly the 1st step is to factor out 3x: 3x(2x^4-17x^2-9) Then you have a quadratic in x^2, which you can factor with a little work, to get 3x(x^2-9)(2x^2+1) The x^2-9 is easy, giving 3x(x-3)(x+3)(2x^2+1)
*November 18, 2015*

**Scientific Calculus**

if your constant is the k in e^-kt, then you have e^-0.000124t = 0.56 Now you can calculate the approximate age. If by constant of proportionality you mean that that fraction is lost each year, then you have 0.999876^t = 0.56
*November 18, 2015*

**geometry**

Not sure how he can turn from the horizontal, unless he goes uphill, but whatever the direction, just turning 30° in the opposite manner will put him on a course parallel to his original one.
*November 17, 2015*

**Math**

m = 3f 5m/6 = b 2/3 f = g b = g+121 So, solve all that and you get m/6 + f/3 = 77
*November 17, 2015*

**Geometry**

XY = √(4h^2+4h^2) XZ = 4h YZ = √(4h^2+4h^2) Now just see whether XY^2 + YZ^2 = XZ^2
*November 17, 2015*

**Algebra 2**

The total value is 355. You have just counted the bills, rather than adding their values. Clearly, n+f+t cannot be both 355 and 120! n+5f+10t = 355 n+f+t = 120 n = 2(f+t) The way you wrote the last equation, you indicated that adding the 5's and 10's you had twice as ...
*November 17, 2015*

**Math**

if A is 62, so is D If B is 13, so is E So, since D+E+F=180, just plug in your values for D and E.
*November 17, 2015*

**Algebra 1**

d = 40 + 65h
*November 17, 2015*

**Radicals**

fractional exponents are roots, where the radical index is the denominator. So, you have n^3/4 p^5/4 = (n^3 p^5)^1/4 = ∜(n^3 p^5) or, if you want proper fractions for the roots, = p∜(n^3 p)
*November 17, 2015*

**Integer Exponents**

minus powers swap between top and bottom in fractions. So, if you want all positive exponents, (6abc^2) / 15a^2 * (2bc / 3a)^-2 = (6abc^2) / 15a^2 * (3a / 2bc)^2 = (6abc^2 * 3a)/(15a^2 * 2bc) = 18a^2bc^2 / 30a^2bc = 3c/5 try the other one the same way. We can check your work.
*November 17, 2015*

**Algebra - eh?**

If the boards are h inches high, then the soil is (h-4)" deep. If the outside dimensions are x and y, with x<y, x=2h y=4h So, the inner dimensions are (x-8) and (y-12), and using the given volume, (h-4)(x-8)(y-12) = 3136 h(2h-8)(4h-12) = 3136 h = 11 inches. Check: The ...
*November 17, 2015*

**Math**

so, did you draw a diagram and see the similar triangles?
*November 17, 2015*

**@Damon - typo**

make that -4z... But I'm sure the student caught the typo.
*November 17, 2015*

**Calculus**

Fx = 3x^2 + 2y^3 Fy = 6xy^2 - 9 Fxx = 6x Fxy = 6y^2 = Fyx Fyy = 12x Now just plug in the numbers
*November 17, 2015*

**ipc**

well, v changes by +3.2 m/s every second. So, what is that after 6 seconds?
*November 17, 2015*

**math plz help**

like terms have the same variable. So, ...
*November 17, 2015*

**Trigonometry**

3 = 3 cis0 2+3i = √13 cis x where tan x = 3/2 now divide, and you get 3/√13 cis(0-x) = 3/√13 (cosx - i sinx) = 3/13 (2/√13 - 3/√13 i) = 6/13 - 9/13 i
*November 17, 2015*

**Trigonometry**

b^2 = a^2+c^2-2ac cosB So, plug in your numbers and solve for cos B Then B is cos^-1 of that number.
*November 17, 2015*

**Trigonometry - eh?**

planes fly on headings distant objects have bearings I thought you said the plane flew SW from C to A. Why then do you ask for it? Typo?
*November 17, 2015*

**Calculus**

Partials are easy. Just consider the extra variables as constants. Wx = 4xy-6yz Wy = 2x^2-6xz+10z^2 Wz = -6xy+20yz Now just plug in the numbers.
*November 17, 2015*

**Calculus**

∂R/∂x1 = 700 - 4x1 - 4x2 ∂R/∂x2 = 700 - 4x1 - 4x2
*November 17, 2015*

**math**

since 2 <= f(x) <= 3, and the width of the interval is 6, 2*6 <= ∫f(x) dx <= 3*6
*November 17, 2015*

**math**

oops: y=64
*November 17, 2015*

**math**

4x = 7y x-y = 48 x - 4x/7 = 48 3x = 7*48 x = 7*16 = 112 So, y = 4*16 = 56 check: 112-56 = 48
*November 17, 2015*

**calculus**

If the pen is x by y, then we have xy=720 p = 2x+y = 2x+720/x dp/dx = 2 - 720/x^2 x^2=360 x = 6√10 So, the pen is 6√10 by 12√10 As always, the area is max when the fence is divided equally among lengths and widths. clearly the cost per foot of the fence does ...
*November 17, 2015*

**VERTEX,FOCUS AND DIRECTRIX**

x^2+3y-9 = 0 x^2 = -3(y-3) now use what you know about the parabola x^2 = 4py to discover the properties. In this case, the vertex is at (0,3).
*November 17, 2015*

**Math**

f(x) = x^3(x^2+7) Now you can easily state the zeroes and their multiplicities.
*November 16, 2015*

**math - linear programming**

If there are x boxes of nuts and y boxes of fruit, you want to maximize p=7x+8y subject to 2x+4y <= 1000 2x <= 900 2y <= 400 Now use your favorite linear programming tool.
*November 16, 2015*

**Calc**

v = 1/3 πr^2 h = π/3 (d/2)^2 h = π/12 h^3 dv/dt = π/4 h^2 dh/dt Now just plug in your numbers.
*November 16, 2015*

**Algebra 2**

correct
*November 16, 2015*

**Duplessiss primary**

well, 97 = 6*16 + 1
*November 16, 2015*

**Geometry**

p>p'(-2,-6) for the glide reflection where the translation is (x,y)>(x,y-1) and the line of reflection is x=1. What are the coordinates of P? The answer is (4,-5) I'm looking for the steps of how to get to the answer. 69-year-old grandpa trying to help grandson
*November 16, 2015*

**Algebra**

if each value of y is the same multiple of x, it varies directly. If you can multiply each value of x by some number, k, and get the corresponding value of y, then k is the constant of variation, and y = kx
*November 16, 2015*

**algebra**

Parallel lines have the same slope. So, you want a line with slope = -1 Now you have a point and a slope. Use that to get y+2 = -1(x-2) y+2 = -x+2 y = -x Or, given y = -x-2, you know that any parallel line will be y = -x + b So, plug in x=2 into your equation, and you have y...
*November 16, 2015*

**math**

divide both sides by -13 what do you get?
*November 16, 2015*

**Calculus**

actually, that's a repeated linear. I get 1/(x+2) + 2/(x+2)^2 - (x-2)/(x^2+4)
*November 15, 2015*

**College Algebra**

just put the words into symbols. If the numbers are x,y,z, respectively, then we are told that y=z+5 x=2y x+y+z=87 Now just solve the equations.
*November 15, 2015*

**math**

|6-4| = |6|-|4| = 6-4 = 2 |4-6| ≠ |4|-|6| = 4-6 = -2 -b is the additive inverse of b, so the statement is always true.
*November 15, 2015*

**Quadratic Functions Applications**

#1 -4t-4.9t^2 = -1750 #2 (w+2*3)((w+6)+2*3)-(w)(w+6) = 288 #3 If Mary Beth takes x hours, 1/x + 1/(x+6) = 1/4 #4 clearly a 9x9 square fits the bill Since a square has maximum area for a given perimeter, no other rectangle can do the job.
*November 15, 2015*