Monday

August 3, 2015

August 3, 2015

Total # Posts: 32,562

**Math**

It's always easiest to convert mixed numbers to improper fractions. for adding, find the lowest common denominator for multiplying, just multiply/divide 9 9/10 × 8 8/9 = 99/10 * 80/9 = 88 15 11/15 + 14 5/9 + 7 3/5 = 708/45 + 655/45 + 342/45 = 1705/45 = 341/9 = 37 8/9...
*May 1, 2015*

**Math**

3^3 = 27, not 18 4 * 27 -54÷6+25 Just as multiplication/division are done left to right, so are addition and subtraction 108-9 +25 99+25 124 Besides the typo of 26, you did 72-(9+26), not 72-9+26 314-3 [2^5 -(9- 4 ) ^2 +3]^2 314-3 [2^5 - 5^2 +3]^2 314 - 3[32-25+3]^2 314...
*April 30, 2015*

**Math**

so, show us your work, and we'll check it.
*April 30, 2015*

**Calculus**

the area of a triangle of side s is √3/4 s^2 So, if the triangles have side x and the tent has length y, we have (√3/4)x^2 * y = 2.2 the area of cloth used is a = 2(√3/4)x^2 + 3xy and the cost c is c = 1.4(2(√3/4)x^2 + xy)+xy Now just find dc/dx, after ...
*April 30, 2015*

**algebra please help**

I only see one polynomial.
*April 30, 2015*

**Trigonometry**

hey, come on. The y-intercept is where x=0! So, just plug it in y(0) = -2 sin(0-pi/2) = -2(-1) = 2 getting x-intercepts can be hard. Getting the y-intercept is trivial! Don't forget your Algebra I now that you're in trig.
*April 30, 2015*

**Trigonometry**

the origin is an x-intercept if f(0) = 0. Is that true here?
*April 30, 2015*

**Advanced Functions**

sin4x/(1-cos4x) (2 sin2x cos2x)/(2sin^2 2x) cos2x/sin2x (2cos^2 x - 1)/(2sinx cosx) cosx/sinx - 1/(2sinx cosx) cotx - 1/2 cscx secx
*April 30, 2015*

**Math**

the diameter is 14, so the radius is 7 the area is π*7^2 = 49π
*April 30, 2015*

**Math**

One way: divide the big volume by the small volume: (3 3/4)(5)(4 1/2) / (1/4)^3 = (675/8) / (1/64) = 5400 Another way: decide how many cubes it takes to fit each of the larger dimensions (3 3/4) / (1/4) = 15 5 / (1/4) = 20 (4 1/2) / (1/4) = 18 So, the prism is 15x20x18 cubes...
*April 30, 2015*

**Math**

y=x+(x/4) ? Why not just 5/4 x? Once you get your curves figured out, r = the distance to the inside curve R = the distance to the outside curve You need to solve for x, so you know r. Clearly, R=3, since that's the far boundary. The limits of integration (along dy) are ...
*April 30, 2015*

**Math**

assuming the cylinder also has diameter 7, then if the cone has height h and the cylinder has height k, you need π/3 * r^2 h = π * r^2 k h/3 = k The cone needs to be 3 times as tall as the cylinder
*April 30, 2015*

**math**

Draw a diagram. You have a 30-60-90 triangle, with the tree at the right angle. You want the altitude from the tree to the road. The distance of the tree from B is 200 The distance of the tree from A is 200√3 So, h = 100√3
*April 30, 2015*

**Calculus**

with 3 unknowns and only two equations, there will be no unique solution. It should be 13y+5z = 39 so, pick any y and z that fit, and then figure x. Or, you can evaluate y and z in terms of x: y = 5x-7 z = 13(2-x) Now you can pick any value for x, and then figure y and z. In ...
*April 30, 2015*

**Math**

1982: (3.35*40+80)(50) = 10700 2015: 10700*1.045^(2015-1982) = 45732.12
*April 30, 2015*

**Math**

317.24(1.085)(1.15)+25.00
*April 30, 2015*

**Calculus**

just add the vectors. That is the resultant, call it r. The equilibrant is -r: that vector which cancels the resultant, keeping things in equilibrium.
*April 30, 2015*

**Calculus**

vectors are just a compact way of describing three independent sets of numbers. You just have 3a-6 = -3 9-2b = 1 6-2b = -2 clearly, a=1, and any value of b will work. since (1,3,2) and (3,b,b) are not collinear, they span R2.
*April 30, 2015*

**Math**

pq-pr-qp+qr-rp+rq or, arranging factors alphabetically, pq-pr-pq+qr-pr+qr -2pr+2qr 23ab-12ab - 12bc^2-13bc^2 11ab - 25bc^2
*April 30, 2015*

**Math**

just plug and chug: 2(-7/2)^2 - 9(-7/2) + 7 ...
*April 30, 2015*

**Math**

nothing to solve. just evaluate the expression 3(-1.3)(2/5) - |-1.3-2| -1.56 - |-3.3| -1.56 - 3.3 -4.86
*April 30, 2015*

**Math**

(3245.50-143.15)(1-0.10) = 2972.115
*April 30, 2015*

**Calculus**

dy/dx = (1+x)/xy y dy = (1+x)/x dx 1/2 y^2 = lnx + x + c since y(1) = -4, ln 1 + 1 + c = 8 c = 7 1/2 y^2 = lnx + x + 7 . . .
*April 30, 2015*

**math**

pi * 9^2 * 4
*April 30, 2015*

**math**

if the digits are a,b,c we see that a=4 Then we are doomed. If b and c are both odd, they cannot sum to 5, which is also odd. And how about a little punctuation? That run-on sentence is very annoying.
*April 30, 2015*

**Algebra 2**

Is there a question in there somewhere?
*April 30, 2015*

**math**

just subtract what was used from the original amount: 9100 - 321*28.286 However, that assumes that all the leftover parts could be combined to form new circles; not very likely. A better way to look at it is to decide how many rows and columns of discs could be cut. 130/6 = 21...
*April 30, 2015*

**SOLVE -MATH**

9C6 * 6C3
*April 30, 2015*

**physics**

we have, since the focal length is constant, 1/f = 1/20 + 1/x = 1/16 + 1/(x+2.7) Just solve for x, and then find f.
*April 30, 2015*

**Calculus**

good work. Confirm with the graphs at http://www.wolframalpha.com/input/?i=plot+x%5E2%2B3x%2B2%2C+y%3D3x%2B2+for+-1+%3C%3D+x+%3C%3D+1
*April 30, 2015*

**maths**

you have a common ratio, so p/-6 = -32/p p^2 = 192 ...
*April 30, 2015*

**math**

No, P(black) = 9/10 1 - 9/10 = 1/10 B is the odds of drawing a white, not the probability.
*April 30, 2015*

**Physics**

1A is 1C/s You have 73mC/9s = 8.11mA the net charge is not relevant here, since all we need is the number of Coulombs.
*April 30, 2015*

**MAT 142**

keeping all the measurements in yards, (15/3)(8/3)(8/36)($30)
*April 30, 2015*

**Math**

clearly you can drop the trailing zeros, getting 504/5940 both are even, so you can factor out 2 top and bottom: 252/2970 and again: 126/1485 now 3's: 42/495 and again: 14/165 That's as far as you can go. Or, you can factor both numbers. 5040 = 2^4 3^2 5 7 59400 = 2^3 ...
*April 30, 2015*

**Math**

(8*7)/2 - π/4*3^2
*April 30, 2015*

**math**

hmmm. None of the polynomials factors over the reals, so I don't see any help there. Looks like GCF=1 and LCM = (1+4x+4x^2-16x^4)(1+2x-8x^3-16x^4)(16x^4+4x^2+1) if x=-1 we have -17,-7,21 x=0 we have 1,1,1 x=1 we have -7,-21,21 x=2 we have -231,-315,273
*April 30, 2015*

**math - eh?**

what's with the .. ?
*April 30, 2015*

**Math**

first expand: 4x^3y+30x^2y-35xy^2-72x^2y+80xy^2-11xy^2 then combine: 4x^3y-42x^2y-34xy^2
*April 30, 2015*

**Math**

(4)(14)+(-1)(3)+(-6)(8) = 56-3-48 = 5 Pretty grim score, eh?
*April 29, 2015*

**English**

What do you do when the author can't be found? How do you cite the book? Would use just the title of the book or explain that the info is missing?
*April 29, 2015*

**English**

what should you do if you need to cite a book for which you don't know the author?
*April 29, 2015*

**Algebra 2**

multiply through by 8x and you have 2(x+2)-3(4) = x 2x+4-12 = x x = 8 check: 10/32 - 3/16 = (10-6)/32 = 4/32 = 1/8
*April 29, 2015*

**Math**

to be a perfect square, all its prime factors must be squared. Since 7 occurs an odd number of times, 7^2 cannot divide the number. So, no, it is not a perfect square. It is almost a perfect square, though, since 2^6 * 3^10 * 5^12 * 1^18 = (2^3 * 3^5 * 5^6)^2
*April 29, 2015*

**Math**

6789 = 3*31*73 since 3,31,73 all divide the first term, and 6,62,146 all divide the second term, 6789 divides both terms, and thus the sum as well.
*April 29, 2015*

**Math**

all the powers must be a multiple of 3. So, it is a perfect cube. It is (2^3 * 3^4 * 5^2 * 7)^3
*April 29, 2015*

**MATH**

d = 7n 10d = 650+5n 10(7n) = 650+5n 65n = 650 n=10 so, d=70
*April 29, 2015*

**Molar mass**

so, what steps did you follow? If you want help with your error, show your work...
*April 29, 2015*

**Mathematics**

just plug and chug: 148225 - x^2 = 578132.1225 - 406278.76 + 1274.8x - x^2 x = -18.535
*April 29, 2015*

**pressure**

PV=nRT Just plug in your numbers and solve for P.
*April 29, 2015*

**math**

440x220 with the 440' side parallel to the river. the related questions below provide steps for the solution.
*April 29, 2015*

**Math**

if it is a perfect square, all of its prime powers will be even. Since if you have (2^a 3^b 5^c ...)^2 all the exponents are doubled.
*April 29, 2015*

**math: fundamental counting principal**

12*10*7*5
*April 29, 2015*

**math; solve problem**

the simplest solution is 32.2*21/13.65
*April 29, 2015*

**Math**

The problem is poorly worded. Why don't you draw a diagram, and tell us what the relevant points of reference are?
*April 29, 2015*

**MATH; STANDARD DEVIATION**

you can plug in your numbers and play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
*April 29, 2015*

**Algebra**

y=0 at x = -1 for x > -1, y is increasing
*April 29, 2015*

**Pressure**

PV=kT, so P/T is constant Figure the increase in T (as a factor), and apply that same factor to P to keep the ratio constant.
*April 29, 2015*

**Math Help**

what, you can't plug in values for n? a1 = 1(1^2-6) = 1(-5) = -5 a2 = 2(2^2-6) ... a1=14 a2 = (-2)(14) = -28 a3 = (-2)(-28) ...
*April 29, 2015*

**Math**

GCF=1 LCM=pq
*April 29, 2015*

**math**

3x2 + 3x5 = 6+15 = 21 8x3 = 18 So, he needs more canvas than he has. Or, you could line up the two desired pieces, and he needs one large piece 3x(2+5) = 3x7, but his piece is only 3x6.
*April 29, 2015*

**algebra NEED HELP**

√(x-5) is always positive. So, there is no solution √(2-7x) = 2x 2-7x = 4x^2 4x^2+7x-2 = 0 (x+2)(4x-1) = 0 so, x = -2 or x = 1/4 But since √(2-7x) is positive, x = -2 is an extraneous solution So, x = 1/4 is the only solution
*April 29, 2015*

**algebra**

since y=kx, y/x is constant. Thus, 14/21 = 7/x
*April 29, 2015*

**Calculus and Vectors**

the resultant is <900/√2,-900/√2 + 100> Now just find the speed and direction.
*April 29, 2015*

**Calculus**

They span R2 if they are independent. That is, the 2nd is not a multiple of the 1st. So, what do you think?
*April 29, 2015*

**Math help Steve?**

right on
*April 29, 2015*

**Math**

well, you need 3x+4 = 16 or 3x+4 = -16
*April 29, 2015*

**Last week Help Math**

now way to tell about the median and mode, but the mean is changed from (10*10000)/10 to (9*10000+20000)/10
*April 29, 2015*

**Calculus**

Draw a diagram of the forces. tanθ = 76/220
*April 29, 2015*

**Math (check answers)**

#1 Nope (C) is (x+3)(x-1)(x-5) You want (x+3)(x+1)(x-5) #2 Nope There are a total of 11 votes, so for is 7/11 = 64%
*April 29, 2015*

**Math help!**

If the vertical lines have length y, and the horizontal sides have length x, then 3y+2x = 270 and the total area is a = xy = x(270-2x)/3 = 90x - 2/3 x^2 This is just a parabola with vertex at (135/2,6075/2), so the total area is 6075/2. Since x=135/2, y=45 Since the inside ...
*April 29, 2015*

**Calculus-limits**

take derivatives top and bottom. The desired limit is the same as the limit of (cosx-0)/1 = cosx Now take the limit as x->a so, (b) is the answer.
*April 29, 2015*

**math**

is that 13 in high? Presumably the circular top has the same circumference as the cylinder.
*April 29, 2015*

**math**

(a+36d)/(a+20d) = 7/4 (a+64d)/(a+36d) = 7/4 3a=4d looks like there are many such sequences: a=12, d=9 T21 = 192 T37 = 336 T65 = 588
*April 29, 2015*

**Algebra**

the angle is x, where tan(x) = 2/(30*12)
*April 29, 2015*

**Mathh**

note that y grows by 3 when x grows by 1. That means you can start with y = 3x But since y(0)=1 instead of 3*0=0, y = 3x+1
*April 29, 2015*

**Calc 1**

If the triangle has side x, then the area a = ((11-3x)/4)^2 + √3/4 x^2 That's just a parabola. Its vertex will be the minimum area. For maximum, check to see which is greater: a(0) or a(11).
*April 28, 2015*

**math**

do you know how to calculate the length of a helix? The radius is 2/π, so we have x = 2/π cos θ y = 2/π sin θ z = 15/4π θ 0 <= θ <= 8*2π
*April 28, 2015*

**calculus**

dy/dx = y^2/x^3 dy/y^2 = dx/x^3 -1/y = -1/(2x^2)+c y = 2x^2/(1-cx^2) what's with all the verbal noise? You want to discuss y' = 2x√(1-y^2)? Just say so dy/√(1-y^2) = 2x dx arcsin(y) = x^2 + c y = sin(c+x^2)
*April 28, 2015*

**Geometry**

the front wheel makes 6/10 of a turn for every turn of the rear wheel. So, the pedals move (6/10)*2pi*7 inches during that time.
*April 28, 2015*

**math**

.5L/s * 3.7gal/L * 3600s/hr = ? gal/hr
*April 28, 2015*

**Calculus**

f(x) = ax^2 + 1/3 for x >= 1 bx - 10/3 for x < 1 so, we need f(1) to be consistent. That is, a + 1/3 = b - 10/3 we also need f'(1) to be consistent: 2a = b so, a + 1/3 = 2a - 10/3 a = 11/3 b = 22/3 a+b = 11
*April 28, 2015*

**Math help**

well, what is (3√2)^3 ?
*April 28, 2015*

**Calculus**

actually, I misspoke. You want p when h=8200, so p(8200) = 101.3 e^(-.000151*8200) You should have caught that typo...
*April 28, 2015*

**Calculus**

dp/dh = kp dp/p = k dh ln p = kh+c p = c*e^(kh) p(0)=101.3, so c=101.3 p(h) = 101.3 e^(kh) p(1000) = 87.1, so 101.3 e^(1000k) = 87.1 1000k = ln(87.1/101.3) k = -.000151 p(h) = 101.3 e^(-.000151h) so, now solve for h when p = 8200
*April 28, 2015*

**Calculus**

120 sin 25° think about it -- a horizontal force (0°) does no lifting, and an upward force (90°) is all lift.
*April 28, 2015*

**Physics - Half Life Question Check!!!**

The amount left after t billion years is (1/2)^(t/1.25) So, you want (1/2)^(t/1.25) = 0.77 t/1.25 log 0.5 = log 0.77 t = 1.25 log(0.77)/log(0.5) = 0.471 Looks like (B) to me.
*April 28, 2015*

**Geometry**

a = 1/4 √3 (36/3)^2
*April 28, 2015*

**Algebra Word Problem**

if there are x price increases, the revenue is (95-x)(100+x) That is just a parabola. Its vertex represents maximum revenue.
*April 28, 2015*

**Calculus**

your logic and your answer are correct.
*April 28, 2015*

**Calc**

wold that not be just the integral of C' from 3500 to 8500? Just use the power rule for each term.
*April 28, 2015*

**Calculus help??**

f(x) = ∫[0,x] 2πu du df/dx = 2πx you are correct. I suspect that those choices belong to a different problem, or that there is a misprint in this one.
*April 28, 2015*

**Calculus I**

The question is, how many can you sell at $10? Let's say it's 1000. Then if there are x price reductions, you can sell 1000+500x So, the revenue will be (1000+500x)(10-x) The cost is 3000+2(1000+500x) profit is revenue - cost. Use your real value instead of 1000, and ...
*April 28, 2015*

**Math Check**

both right
*April 28, 2015*

**Math Check**

Both look good to me.
*April 28, 2015*

**math**

the left side is also just a difference of two squares, so ((a-3)+(a-2))((a-3)-(a-2)) = (2a-5)(-1) so, you have 5-2a = 5 a = 0
*April 28, 2015*

**Math**

it's a problem in exponential growth similar ones in exponential decay are things like radiocarbon dating, where the amount of carbon-14 diminishes each year by a certain small percentage.
*April 28, 2015*

**Math**

after t minutes, there are 2^(t/15) bacteria. So, find t when 2^(t/15) = 10000 t/15 log2 = log10000 t = 15 * (log10000/log2)
*April 28, 2015*

**math**

if the side of the base is s, then you know that 10s^2 = 810 The total area is the base (x^2) and 4 sides, each of area 10x.
*April 28, 2015*

**math**

the base is 18*18 each side is a triangle of base 18 and height 12, so the faces have area 4*(18*12/2) SO, just do the math.
*April 28, 2015*