Wednesday

April 23, 2014

April 23, 2014

Total # Posts: 21,927

**algebra**

almost always you can take "of" to mean "times" 25% of 200 = .25 * 200 = 50

**percentages/word problem**

(1-.30)p 72.09 p = 72.09/.70 = 102.98

**physical science**

If You Were Riding A Train List Some Examples Of Items That Would Make It Seem Like You Weren't Moving

**math**

looks like there was a 20% discount, plus 6% tax.

**Math**

Note that 4x^2 and 9 are both perfect squares, so the first thing I'd try is (2x+3)^2 good guess!

**Math - Int Trig**

I'll do one. Do the others in like wise. If you get stuck, come on back with what you did. (g∘h) = 3/(h^2+2) = 3/(x-2+2) = 3/x (g∘h)(-2) = 3/-2 = -3/2 The domain of h is x>=2 The domain of g is all reals, since x^2+2 is never zero. So, the domain of (g∘...

**Algebra**

the common denominator is (b+1)(b+2)(b-2), so when you place all over the common denominator, you have [4(b^2-4) + 1(b+1) + 5(b+1)(b-2)]/[(b+1)(b^2-4)] (9b^2-4b-25)/(b^3+b^2-4b-4)

**PRE CALC**

cos k*pi = 1,-1,1,-1 so they add to zero and the sum is just 4

**Algebra**

(x^3)^-4 = x^-12 (-2x^-2)^-3 = (-2)^-3 (x^-2)^-3 = -1/8 x^6 multiply those and you have -1/8 x^-6 = -1/(8x^6)

**Math**

so, what's the problem? 2 2*159 = 318 3 ... 5 10

**math - 6th grade**

subtract 3x+2 from both sides and you have 4x+2 -3x-2 = 3x+9 -3x-2 x = 7

**Math**

Tn = -3n

**Math**

subtract 3 for each successive term. So, by the 93rd term, you have done it 92 times. -3 - 3*92 = -279

**Math**

I don't see any equations (gotta have an = sign for that) add 4 for each term. So, for the 76th term, you have added 4 75 times, and it is thus -2 + 75*4 = 298

**Geometry**

Each lateral face is a rectangle. The trapezoid has four sides, possibly all different, so you have four rectangles. Then add the areas of the two trapezoidal bases.

**Geometry**

well, duh - it's the area of the triangular base. If you're discussing prisms, you've surely already covered triangles, no?

**Math**

looks like y = 2 - x/2 Note that y decreases by 1 when x increases by 2, making the slope -1/2

**math**

subtract the smaller rectangle from the larger. The remainder is the area covered by the frame. 28*24 - 24*20 = ? or, rewriting things a bit, 28*24 - 20*24 = 8*24 = ?

**math**

If you look at the table, you should find a value of 1500(1+.12/4)^(4*8) = 3862.62

**math**

3500((1+.12/4)^4 - 1) = 439.28

**geometry maths**

well, of course, the larger circle has radius 1. Draw a diagram of the upper right quarter of the square. Include half the diagonal of the square, which goes through the centers of the two circles (O and Q), which are tangent at point P. Draw a vertical diameter of the smaller...

**Calculus**

20^n = 5^n * 4^n so, you have 5^n/20^n + 4^n/20^n = 1/4^n + 1/5^n both of which converge

**Calculus**

sure you do. It's just a geometric series a = 1/e^2 r = 1/e^2 S = a/1-r = (1/e^2)/(1 - 1/e^2) = 1/(e^2-1)

**Algebra 2**

division by zero is not defined. So, when the denominator is zero, f(x) is not defined. x^2-4x+3 = (x-1)(x-3) so, when x=1 or 3, you are trying to divide by zero. Those values are not part of the domain. Note that x^2-9 = (x-3)(x+3) So, for any value except x=3, f(x) = (x+3)/(...

**Math**

just determine how long each call was, then add them up. 10:15-11:00 = 45 minutes 12:30-1:15 = 45 minutes total = 90 minutes

**math**

2 1/4 + 1 1/2 = 3 3/4

**Math**

240*8*40 = 76800 just divide 8,000,000 by that

**Maths please someone help me out!!!**

.2^(t/4) multiplies by 0.2 every time t increases by 4. That's how the efficiency is described in words. so, get out your calculator (online or physical) and evaluate some values for t. As a sanity check, 50% is a little more than twice as much as 20%, so expect t to be so...

**geometry - eh?**

a circle has only a radius, not an inradius and a circumradius.

**maths**

have you a calculator? Just punch in the numbers.

**geometry - wow**

heck, I don't even have a diagram!

**maths**

a^2 + b^2 = 16 2ab = 7 (a-b)^2 = 16-7 a-b = ±3

**mathematics**

3x^2+6x-2 = 0 better use the quadratic formula. x = (-6±√60)/6

**mathematics - eh?**

gotta clean up those ? marks with + or - signs.

**Algebra**

e^2-e-12 = (e-4)(e+3) dividing by e-4 leaves e+3 similarly, a^2+11a+30 = (a+5)(a+6) x^2+3x+2 = (x+1)(x+2) x^2+5x+6 = (x+2)(x+3) now the LCM should be easy

**Maths**

84+65+76 = 225 to have an 80 average of 4 tests he needs 320 total points. good luck, Jim.

**High school math**

last I checked, 2+2=4

**High school math**

I assume you're just making a test post...

**math**

depends on the shape. Unless the base is square, there's no way to find the other two missing values.

**geometry**

I'd say it's h 487 = 25/3 pi h

**Algebra**

heck, the answer to the 2nd part provides the answer to the first part: x y ∆y 1 3 2 10 7 3 29 19 4 66 37 5 127 61 6 218 91 as you can see, x has to increase less and less for y to double.

**Algebra - bizarre**

now this is getting weird. Another person assuming that sqrt(...) is the exact notation? Go ask the person who gave you this, to show you the solution we already posted.

**Calculus**

dy/dx

**Calculus - oops**

rats - that's dx/dt = -6csc^2θ dθ/dt when θ=π/3, we have x = 6/√3 and cscθ = 2/√ dx/dt = -6(4/3)(-π/3) = 8π/3 km/min

**Calculus Help**

At t=0, let x=0, so that at time t, x/6 = cotθ x = 6cotθ dx/dt = -6sec^2θ dθ/dt when θ=π/3, we have x = 6/√3 and secθ = 2 dx/dt = -6(2)(-π/3) = 4π km/min

**Calculus Help Please!!! Check**

Odd notation. P is a point (x,y) so usually we would see dy/dx = 3y y = c*e^3x 2 = c, so y = 2e^(3x) You divided the right side by 3 and multiplied the left aside by 3, but that was not correct: dy/dp = 3y ∫dy/y = ∫3dp ...

**calculus help thanks!**

PV = nRT V dP/dt + P dV/dt = nR dT/dt Now just plug in the data: (14)(0.13) + (8.0)(-0.17) = (10)(0.0821) dT/dt dT/dt = 0.56 °K/s

**math**

4 s's out of 11 letters, so ...

**math**

what are the odds i favor of picking an S in Mississippi?

**Algebra II**

draw the lines for the equations For the first one, shade the area below the (dashed) line, since y is less than 2x-9 For the second one, shade the area above the (solid) line, since y is greater than or equal to 3-5x.

**Physics**

v = Vo + at s = Vo*t + 1/2 at^2 12 = Vo + 10a a = (12-Vo)/10 100 = Vo*10 + (12-Vo)/20 * 100 100 = 10Vo + 5(12-Vo) 100 = 5Vo + 60 Vo = 8

**algebra 2**

just substitute: 16x^2 - 96x + 5(16x^2-64) = 256 16x^2 - 96x + 80x^2 - 320 = 256 96x^2 - 96x - 576 = 0 x^2 - x - 6 = 0 (x+2)(x-3) = 0 Now you have x, get y. see the solution at http://www.wolframalpha.com/input/?i=solve+16x^2-5y^2%3D64%2C+16x^2%2B25y^2-96x%3D256

**maths**

a^2 + b^2 = 16 2ab = 8 (a+b)^2 = 24 so, a and b will not be integers. Their sum is √24 or -√24, and both will have the same sign, since ab > 0. b = 4/a, so we have a^2 + 16/a^2 = 16 a^4 - 16a^2 + 16 = 0 a = ±2√(2±√3) b = ±(√...

**math**

the garden is 10x10, so what's the perimeter?

**math**

correct. The power set of A P(A) is the set of all subsets of A. These would be {}, {2}, {3},...{2,3},{2,5},... and so on up to A itself.

**math**

well, how many elements in A?

**Algebra II**

Since speed * time = distance, we have (with jet=j and wind=w): 7(j-w) = 3220 3(j+w) = 2820 j=700 w=240

**algebra**

y = 6.2x + b 2222.4 = 6.2*52 + b, so b = 1900 So, we now know that y = 6.2x + 1900 Just plug in x=26 Or, without even finding b, we know that each gallon of fuel weighs 6.2 pounds, so just subtract 26*6.2 from 2222.4

**Astronomy**

since arc length s = rθ, just plug in the numbers: 7.4*10^3 * 6.3 * 1/3600 * pi/180 = 0.226 Kpc

**calcules**

elasticity e = df/f ÷ dp/p = df/dp * p/f df/dp = A(-0.13)p^(-1.13) so, e = -0.13Ap^(-1.13) * p/A p^(-0.13) = -0.13/p^0.26 so, we have negative elasticity, meaning that demand will go down if price goes up. It also shows that for larger prices, the elasticity changes, be...

**Math**

a=b b+2b = 6(a-26) 3b = 6(b-26) 3b = 6b - 156 b = 52 So, they both started out with 52 cupcakes.

**mathematics**

the distance from (-2,4) to the line 2x-3y-10 = 0 is 2√13, so that's the radius of the circle. (x+2)^2 + (y-4)^2 = 52 you can see this at http://www.wolframalpha.com/input/?i=plot+%28x%2B2%29^2+%2B+%28y-4%29^2+%3D+52+and+2x-3y%3D10

**math**

six sides, so make sure there are 2 odd numbers.

**math**

$10 is tax. 50% of that is $5, so reduce the cost by that much. What % of 90 is 5? Just wondering -- where is the profit needed to make money?

**math**

a < c a+c = 29 m = a+26 we want maximum value for alvin, because that will also give the max to melvin. Since a<c, alvin has to have less than half of their shared 29. So, a <= 14 a=14 c=15 m=40 max total: 69

**math**

a+50 = 2b b+50 = 2a (a+b)+100 = 2(a+b) a+b = 100

**math**

center at (0,0) a^2+b^2 = c^2 c = √85

**Calculus Help Please!!!**

well, f(x) is only defined on 0 <= x <= 1 Visit http://rechneronline.de/function-graphs/ and enter 8x*sqr(x-x^2) for your function. Set the range of y to be 2.5 to 3 and the peak will be quite clear

**Calculus Help Please!!!**

f(x) is differentiable on the interval. So, you know there is a c such that f'(c) = (f(2)-f(0)/(2-0) = (-1-2)/2 = -3/2 So, just solve for c in 4c-5 = -3/2 c = 7/8 as a check, view http://www.wolframalpha.com/input/?i=plot+y+%3D+2x^2-5x%2B1+and+y+%3D+%28-3%2F2%29%28x-7%2F8%...

**Algebra**

so, if you have √(y+3) - 4 = 5 √(y+3) = 9 y+3 = 81 y = 78 by the way, I meant that you could have written sqrt(y+3), not just show ... as the argument.

**Algebra**

try √ to copy/paste. as written, I read y+3-4 = √5 but that seems unlikely. You can also write sqrt(...) to show explicitly what is inside the radical.

**algebra**

after the nth year, it is worth 1000(1+.06)^n

**Algebra II**

well, r^2 = 4785^2+1140^2, so the circle's radius is 4919 feet. x^2+y^2 = 4949^2 Now just use your knowledge of the areas of circles and squares to answer the questions.

**Algebra Question~!**

just solve for h=0. -16t^2 + 200 = 0 16t^2 = 200 t^2 = 25/2 . . .

**geometry**

Draw a diagram, showing the altitude. Consider the sine of 1/2 the vertex angle. Its opposite side is half the base, and its hypotenuse is the slanting side. So, sin(θ/2) = 14/22

**geometry**

as with any quadrilateral, you get a parallelogram. This topic is discussed here: http://jwilson.coe.uga.edu/EMT669/Student.Folders/Dozier.Cynthia/essay1/Essay.html

**calculus**

max area for a given perimeter is a circle. Is the wire evenly divided? If so, c = p/2, so r = p/4π, and the total area is a = 2(πr^2) = 2π(p^2/16π^2) = p^2/8π If not, then if we have a tiny circle, (area effectively zero), then r = p/2π and a = &...

**college math**

1 - .85^5

**Calculus**

Looks good to me. I get ∫[1,2] (3-x) - 2/x dx = 3x - 1/2 x^2 - 2logx [1,2] = 3/2 - 2log2 gotta be a typo in the answer. 2log2 is correct.

**arithmetic**

oops. That would be 4,8,12,...

**arithmetic**

1,4,8,...

**math**

35 44

**algebra**

h(t)=0 when t = 1.5

**Programing**

I see a bunch of syntax errors, and no reference to cin >> x[i]. Before trying to debug your logic, make sure to get it to compile.

**Programing**

what's with the cout? you need x2[i][j] = x1[i][j] i goes from 0..2 and so does j. x1 and x2 are the arrays, not the bounds on i and j.

**Algebra**

2√(5L) = 60 √(5L) = 30 5L = 900 L = 180

**Physical Science 9**

what sequence of process must happen for an atom of carbon to go from a man to a car?

**math**

15(3 1/5) = 15*3 + 15*(1/5) = 45 + 3 = 48

**math**

If I pay, I don't get paid nothin'.

**Math**

y = a/c because as x gets huge, only x^2 matters. y = (a + b/x^2)/(c + d/x^2) as x gets huge, the fractions go to zero.

**geometry**

10^6 * 4/3 pi (.005^3) * 2 = pi/3 = 1.047 m^3

**Math**

#1 - forget about the blue pencils. There are 8 yellows in each package. So, in 426 packages, there are 8*426=3408. Note that the title of the problem set was "Multiply a 3- digit number by a 1- digit number". That should have been a clue that your approach was wrong...

**math**

well, yes, as I said. So, just work it out: 600 mi * 5280ft/mi * 12in/ft = 38,016,000 in Note how the units cancel, leaving you with just inches.

**math**

you know the circumference of the tire is 24pi or 75.4 inches. So, figure out how many inches there are in 600 miles, and divide that by 75.4 That's how many times the tire went around.

**Algebra**

you can get excellent graphing help here: http://rechneronline.de/function-graphs/ but you need to enter functions of x. So, solving for y, you have y = (5x+36)/3 y = (26-3x)/5 Enter those two functions and set the range on the y-axis to -10:10 and you will see the solution.

**Calculus**

Good idea. However, in an attempt to use your math, and also to apply to a possibly more general problem later, try implicit differentiation: x^2 + y^2 = 18 2x + 2yy' = 0 y' = -x/y So, if -x/y = 1 and x^2+y^2 = 18, 2x^2 = 18 x = ±3 Now, figuring y should not be ...

**Calculus: Integral**

recall that sec^2 = 1+tan^2, so you have ∫sec^4(4x) dx = ∫sec^2(4x)(1 + tan^2(4x)) dx = ∫sec^2(4x) dx + ∫tan^2(4x) sec^2(4x) dx = 1/4 tan(4x) + (1/4)(1/3) tan^3(4x) and you can massage that in several ways.

**math**

Glad to help. Translating words into symbols can be tricky, but the key is just to examine the data carefully. Believe it or not, it gets easier with practice, just like everything else.

**math**

2w + b = 36 2w + 2b = 56 well, since she walks 2 hours in each case, it is clear that the extra hour of biking gave her an extra 20 km. b = 20 so, since 2w+20=36, w=8

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