Tuesday

March 31, 2015

March 31, 2015

Total # Posts: 30,216

**Math**

(4x^2)^-1 = 1/4x^2 (-2x^-2)^-3 = (-2)^-3 * x^6 = -x^6/8 (1/4x^2) / (-x^6/8) = -8/4x^8 = -2/x^8 (-2/x^8)^-2 = x^16/4
*February 7, 2015*

**Algebra 2**

recall that (a-b)(a+b) = a^2 - b^2 (√3-√2)(√3+√2) = 3-2 = 1 so, you have (1+√3)(√3+√2) = √3+3+√2+√6
*February 7, 2015*

**Algebra 2**

√(3y^3)*√(4xy^4)*√(6x^5y^2) = √(72x^6y^9) = √(36x^6y^8)*√(2y) = 6x^3y^4 √(2y)
*February 7, 2015*

**algebra**

(2+2x)(3+2x) = 7
*February 7, 2015*

**dot product of vecotrs**

oops. Flipped a sign: =3(-1,-3,1)+(2,4,-5)dot 2(2,4,-5)-4(-1,-3,1) =(-3,-9,3)+(2,4,-5)dot(4,8,-10)+(4+12,-4) =(-1,-5,-2)dot(8,20,-14) = -8-100+28 = -80
*February 7, 2015*

**math**

no the prime factors are already listed.
*February 7, 2015*

**Algebra**

3s+4f <= 50 2f <= 13+3s so, 4f <= 6s+26 3s+4f <= 3s+6s+26 <= 50 9s <= 24 s <= 8/3 So, since the smallest s gives the largest f in 3s+4f <= 50 8 + 4f <= 50 4f <= 42 f <= 21/2 Max f is 21/2
*February 7, 2015*

**factorization**

well, you can move 5+5 or 2+13 or 3+3+3
*February 7, 2015*

**precal**

I thought so, but thought I'd check. 1/[√(y^2+y+1) - √(y+1)] multiply top and bottom by √(y^2+y+1) + √(y+1) and you have [√(y^2+y+1) + √(y+1)]/(y^2+y+1 - (y+1)) = [√(y^2+y+1) + √(y+1)]/(y^2-1) So now, a couple of applications...
*February 6, 2015*

**precal**

Do you mean [3y^2/√(y^2+y+1)] - √(y+1) or 3y^2 / [√(y^2+y+1) - √(y+1)] ?
*February 6, 2015*

**Math**

complex numbers cannot be ordered using the conventional operators. However, |z| < |w|
*February 6, 2015*

**Calc**

or, you can let u = 2x-3 dx/du = 1/2 dy/du = dy/dx * dx/du = (6x)(1/2) = 3x Reiny: there's a typo in your 2nd paragraph: y = 3(u+3)^2-2
*February 6, 2015*

**math**

(x+7)(x-6)
*February 6, 2015*

**math**

If she sold x at $12/3, then the rest (144-x) were sold at $6/2. So, x(12/3)+(144-x)(6/2) = (144)(10/6)(1.65) x = -36 Negative pineapples? How is that possible? Look: she paid 10/6 = $1.67 per pineapple. Some she sold at $4 each, and some at $3 each. To make 65% profit, she&#...
*February 6, 2015*

**math**

Hmm. Looks good to me. Did they want you to expand the polynomials? 6561x^3-2187x^2+243x-9 ---------------------------------- 81x^2-18x+2 Or, since you flipped the limits of integration, that would change the sign of the answer, so it'd be +9*...
*February 6, 2015*

**College Physics**

the vectors are <10,0> <0,-20> <-20,0> <0,30> <0,20> Add 'em up and you have <-10,30> Now just convert that to polar form.
*February 6, 2015*

**math**

index 8 means 8th root, or 1/8 power so, you have (5^2)^(1/8) = 5^(2 * 1/8) = 5^(1/4)
*February 6, 2015*

**Geometry**

1/4 pizza, I guess.
*February 6, 2015*

**algebra**

aw, shucks. >scuff scuff< we aim to please, ma'am.
*February 6, 2015*

**algebra**

a^2-a-2 = (a-2)(a+1) a^2-7a+10 = (a-2)(a-5) So, the first fraction is just (a+1)/(a-5) a^2-2a-3 = (a-3)(a+1) a^2+5a+4 = (a+4)(a+1) So, the 2nd fraction is just (a-3)/(a+4) Now you have (a+1)/(a-5) - (a-3)/(a+4) putting it all over a common denominator of (a-5)(a+4), the ...
*February 6, 2015*

**Math**

1/5(2x-10) + 4x = -3(1/5x + 4) first, get rid of those pesky fractions by multiplying by 5: 2x-10 + 20x = -3(x+20) 22x-10 = -3x - 60 25x = -50 x = -2
*February 6, 2015*

**help math**

well, did you check it? 3*1+7 = 10 -11 + 2*1 = -9 Bzzzt, but thanks for playing 3x+7 = -11+2x subtract 7+2x from both sides and you have x = -18 check: 3(-18)+7 = -47 -11+2(-18) = -47 That's better. So, how did you come up with 1?
*February 6, 2015*

**physics**

R=E/I = 1.30/.665 = 1.955Ω Of that, 0.182+0.139=0.321Ω is in the batteries. So, the lamp contributes only 1.634Ω
*February 6, 2015*

**math**

multiply each average score by its weight, and add them up. quizzes: 66.25 Labs: 77.375 Now weight the scores as indicated: 0.05*66.25 + 0.20*80 + 0.20*70 + 0.15*77.375 + 0.15*85 + 0.25 * 75 = 76.42 You do it this way because if all the weights (percentages) add up to 1, then ...
*February 6, 2015*

**math**

I assume you mean sin(5/2 x) = -1/2 so, 5/2 x = 210 or 330 or 570 ... x = 84 or 132 or 228 ... We have to stop at 180, so 84 and 132 are the solutions.
*February 6, 2015*

**Math**

pretty close. I got 5.451 Double check, and keep 3 digits after the decimal point, as instructed.
*February 6, 2015*

**IPC**

v = 43 - 0.28a so, what is a if v=0?
*February 6, 2015*

**algebra**

clearly, if the line contains (0,0), x+y=0
*February 6, 2015*

**math**

If there are 4x kg of maize and 3x kg of beans, then we have 1.3(4*4/7 + 2*3/7) = $4.09/kg check: 4kg at $4 = $16 3kg at $2 = $6 4.09*7 = $28.63 = 1.3 * $22
*February 6, 2015*

**Mathematics**

aside from 6^2 + 2^6 = 10^2 I can't think of any others. My number theory skills are not sufficient for me to come up with a proof. What unit are you studying for this? It might give me a clue.
*February 6, 2015*

**math**

#4 cannot be correct y increases, then decreases, then increases again. However, if y(2) = -2, y = x^2-6 For #5, clearly (a) and (b) are out. Since 5 = 1+4, (c) must be correct, but there is a other huge typo. y(2) = 8, NOT y(7)
*February 6, 2015*

**math**

(3/5)(0.80) + (2/5)(1+p) = 1.10 p = 0.55, or 55% markup
*February 6, 2015*

**Calculus**

hmmm. you keep the details pretty close, eh?
*February 6, 2015*

**factorization**

3*5*7 = 105 now any multiple of 105 has them as prime factors.
*February 6, 2015*

**math**

y(6) = 2, so y = -2(x-6)+2 = 14-2x for 0 <= x <= 7
*February 6, 2015*

**math**

His increments each year were 0,x,2x,3x,4x, summing to 10x So, 10x = (32400-6000)/5
*February 6, 2015*

**algebra**

7x + 3x + 90 = 180 10x = 90 x = 9
*February 6, 2015*

**math**

correct does the answer i convert right? yes, but your English needs some work.
*February 6, 2015*

**math -hw help**

√3 s^2 = 3/2 s^2 = √3/2 clearly, s is not rational √3s^2 = 4√3 s^2 = 4 s = 2, a whole number. Now you try the other.
*February 5, 2015*

**geometry**

using similar triangles, 1.5/8 = FG/(32+8)
*February 5, 2015*

**algebra**

(2x+5)/(x^2+3x+2) - (x+4)/(x^2+3x+2) = (2x+5-x-4)/(x^2+3x+2) = (x+1) / (x+1)(x+2) = 1/(x+2)
*February 5, 2015*

**calculus**

y = 18/√x = 18x^(1/2) y = √(18/x) = 3√2 x^(1/2) Hard to tell what you meant, with that trailing √ sign. Do you write 2x+ to mean 2+x as well?
*February 5, 2015*

**Trig**

sinx/cosx(sinx+cosx/sinx×cosx) As written, it's sinx/cosx (sinx + (cosx/sinx) * cosx) which I doubt is what you meant. I expect you wanted (sinx/cosx)*((sinx+cosx)/(sinx*cosx)) = sec^2x (sinx+cosx) which is not secx. so, what do you really mean?
*February 5, 2015*

**Trig**

try tossing in some parentheses to make it clear just what is in the denominators...
*February 5, 2015*

**Calculus**

∫3√x (2x^2-4) dx If we let u = √x du = 1/2√x dx x = u^2 and we have ∫3√x (2x^2-4) dx ∫6x (2x^2-4) dx/2√x ∫6u^2(2u^4-4) du and that's just power stuff.
*February 5, 2015*

**math**

assuming positive integer n, n even and x negative cannot be evaluated in real numbers. As in ∜(-3) or √(-17) If we allow any real values for n, then things get more complicated. Of course, any negative power of 0 is undefined.
*February 5, 2015*

**Calculus**

the anti-derivative of the integral? You want to integrate twice? I'll just go with ∫(7tan^2x+12) dx ∫(7sec^2x-7+12) dx ∫(7sec^2x+5) dx and that's elementary, right
*February 5, 2015*

**Calculus**

(a) treat x and y as constants and you have 5x^4m^4 + y^3 (b) v' = 6t+8 v" = 6
*February 5, 2015*

**Calculus**

just divide each term by t^4 and you have 7/t^2 + 6/t^3 - 15/t^4 If that doesn't look familiar, think of it as 7t^-2 + 6t^-3 - 15t^-4 and then just apply the power rule as normal.
*February 5, 2015*

**Calculus**

f" = x^2 f' = 1/3 x^3 + c f'(0)=3, so c=3 and f' = 1/3 x^3 + 3 Now do that again going from f' to f.
*February 5, 2015*

**College Algebra**

in each case, all the 1st coordinates are the domain, and the 2nd coordinates are the range. If no element of the domain appears more than once, it is a function.
*February 5, 2015*

**Algebra**

If x is at 3%, the remainder (9000-x) is at 2.6%. So, add up the interest: .03x +.026(9000-x) = 250
*February 5, 2015*

**Math**

correct. It is a polynomial: y = -x^3
*February 5, 2015*

**algebra**

Assuming a month is 4 weeks, after x weeks, Sparky weighs 4 + (5/2)(x/4) So, when do you have 4 + 5/8 x = 14 That is the number of weeks, not months. Clearly it is linear, not exponential. (2.5 lbs/month)
*February 5, 2015*

**Maths**

a+b+c+d = 116 a+5 = b-4 = 3c = d/2 22,31,9,54
*February 5, 2015*

**Algebra II**

√-18x^5y^4 = √9x^4y^4√-2x = 3x^2y^2√2 i
*February 5, 2015*

**Calculus**

You have ∫√((x-1)/x^5) dx = ∫√((x-1)/x) 1/x^2 dx If you let u = (x-1)/x du = 1/x^2 dx and you have ∫√u du = (2/3) u^(3/2) = (2/3) ((x-1)/x)^(3/2) + C
*February 5, 2015*

**Maths Problem**

a = b+x m = b+6 a+b+m = 9x (b+x)+b+(b+6) = 9x 3b+x+6 = 9x 3b = 8x-6 b = (8x-6)/3 I guess you can finish it off now.
*February 5, 2015*

**chemistry**

PV=kT Since P is constant, V/T = k/P is constant if V is decreased by a factor of 361/400, T must decrease by the same factor to have the quotient remain constant. 298.15 * 361/400 = 269.08K It seems odd that the temperature goes down as the gas is squeezed, but remember that ...
*February 5, 2015*

**algebra**

5/(1/2 * 4/7) = 17.50
*February 5, 2015*

**math**

you want the slope of the line through (-3,-4) and (-5,6) That is 10/-2 = -5 Not quite sure why the negative time values. I guess that means minutes before noon.
*February 5, 2015*

**algebra**

37 @ $1 = $37 so, there are $14 extra. That means there were 14 $2 and 23 $1 coins.
*February 5, 2015*

**english?**

yes, that's sort of like English.
*February 5, 2015*

**math**

2(w + 2w+6) = 102
*February 5, 2015*

**math**

pi * (100/2pi)^2 = 2500/pi ft^2
*February 5, 2015*

**math**

correct, except for the spelling of phrase.
*February 5, 2015*

**math**

6(-3) = -18
*February 5, 2015*

**math**

since the angle from 240-180=60 feet away is 45 degrees, the height is 60. SO, if the angle is x, we have tan(x) = 60/240 Now just find x.
*February 4, 2015*

**math**

v(t) = 30-32t so, when is 30-32t = 10 (going up)? 30-32t = -10 (coming down)?
*February 4, 2015*

**Survey of Calculus**

That is correct.
*February 4, 2015*

**math**

must be 42
*February 4, 2015*

**solid**

CS=5, so the distance is √(25+144) = 13
*February 4, 2015*

**math - eh?**

and the answer is . . . 42
*February 4, 2015*

**Math**

Depends on the dimensions of the patio, and whether partial stones (after cutting) may be used. Just the simple answer is 24*100^2/30^2 = 267.7 stones.
*February 4, 2015*

**Math**

after h hours, you want √((18h)^2+(24h)^2) = 150 30h = 150 h = 5
*February 4, 2015*

**math 4th grade**

3 1/2 + (2+ 4 1/2) 3 1/2 + 4 1/2 + 2 3 + 1/2 + 2 + 4 + 1/2 3+2+4 + 1/2 + 1/2 9 + 1 10 or, you can rearrange the numbers in other ways.
*February 4, 2015*

**math**

If each notebook cost x, then 3x + 2*3.95 + 1.23 - 0.75 = 15.85 Now just solve for x.
*February 4, 2015*

**Math**

just start working your way from the inside out. How far do you get? for example, [(4x^2)^-1]^-2 = (4x^2)^(-1 * -2) = (4x^2)^2 = (4)^2 (x^2)^2 = 16x^4 do each factor like that and then simplify.
*February 4, 2015*

**Calculus 2**

you are correct. My bad. Good catch.
*February 4, 2015*

**Calculus 2**

∫ e^x √(1+e^(2x)) dx Note that if u = e^x, you have ∫ u√(1+u^2) du Now, if v = 1+u^2, dv = 2u du, and you have 1/2 ∫ √v dv That I think you can handle, eh?
*February 4, 2015*

**Math**

#1 x^2 = 2x-1 x = 1 #2 2(x-1) = 3x+1 x = -3
*February 4, 2015*

**Math**

(2+2+2)/2 - 2 = 1 2+2+2 - 2/2 = 5 2+2+2 + 2/2 = 7 2*2*2 + 2/2 = 9
*February 4, 2015*

**Math**

1 false a^x is exponential, for any positive a. #2 false, since 1^x is constant.
*February 4, 2015*

**Calculus 2**

(x^3+5x^2+12)/((x^2)(x^2+4)) = (x+2)/(x^2+4) + 3/x^2 So, ∫(x^3+5x^2+12)/((x^2)(x^2+4)) = ∫ (x+2)/(x^2+4) + 3/x^2 dx = 1/2 log(x^2+4) + arctan(x/2) - 3/x + C
*February 4, 2015*

**Math**

Nope. try 4n-6 < 0.5(-n) "opposite" is a vague term. Usually it means negative. You have interpreted it as reciprocal. In either case, "the product of four and a number" is 4n six less than that is 4n-6, not 6-4n.
*February 4, 2015*

**physics**

both are 3 significant digits.
*February 4, 2015*

**Math**

why divide? Just add up all the times. Dividing by 4 will give the average time per activity, but no one asked for that. Dividing 4 by the sum is meaningless. It gives the number of activities that can be done in a second, but that's of no use to anyone.
*February 4, 2015*

**math**

2/5 + 1/6 + 1/3 = 12/30 + 5/30 + 10/30 = 27/30 So, what's not covered?
*February 4, 2015*

**Algebra**

23 nickels is right, but that wasn't what you were asked to find.
*February 4, 2015*

**From Theory to practice**

Q: What's the difference between theory and practice? A: In theory, there is no difference, but in practice, there is!
*February 4, 2015*

**algebra**

(4x+6)(4x-6) = 16x^2-36
*February 4, 2015*

**Math - Absolute Value Inequalities**

B is correct. |x-2| means the difference between x and 2. That difference must be less than 3, so 2-3 < x < 2+3 -3 < x-2 < 3
*February 4, 2015*

**math**

4^2 = 16 5^2 = 25 so, 4.5 is a good first guess. 4.5^2 = 20.25 too big 4.4^2 = 19.36 4.45^2 = 19.80 4.46^2 = 19.89 4.47^2 = 19.98 4.48^2 = 20.07 So, you want something between 4.47 and 4.48 keep going.
*February 4, 2015*

**College Alegbra**

w(2w-7) = 400
*February 4, 2015*

**trig**

who is r? If x is the angle between p and q, then 12^2 = 8^2+10^2-160cos(x) Now subtract x from q's heading (not bearing!)
*February 4, 2015*

**geometry**

since the linear scale has doubled, the volume has grown by a factor of 8.
*February 4, 2015*

**Algebra 1B**

surely your text has examples and explanations. And remember that google is your friend.
*February 4, 2015*

**algebra**

for F(x) = ax^2+bx+c, the vertex lies on the axis of symmetry, at x = -b/2a. so, for your function, that is at x = -2/-2 = 1 f(1) = 7 so, the vertex is at (1,7). See the graph at http://www.wolframalpha.com/input/?i=-+x^2+%2B2x+%2B+6 Recall that the quadratic formula says that...
*February 4, 2015*

**algebra**

there are oodles of online graphing utilities. wolframalpha.com desmos.com come to mind. Just type in your function.
*February 4, 2015*

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