Tuesday

May 31, 2016
Total # Posts: 40,910

**Algebra**

3 ∑ k^2 k = -1
*May 15, 2016*

**Geometry**

atsa right
*May 15, 2016*

**Algebra**

note that the numbers grow by 3's. So, the sequence is 3k+ something. 3*1=3, but the first term is 5, so the terms are 3k+2 The sum is thus 4 ∑ 3k+2 k=1
*May 15, 2016*

**math NEED HELP**

4^3 * 4^4 / 4^9 = 4^7/4^9 = 1/4^2 or, 4^(3+4-9)
*May 15, 2016*

**Algebra**

it is clearly C, because (7x-14) = 7(x-2) but you cannot have a denominator of zero. So, while the fraction is equal to 7 almost everywhere, the value of x=2 is excluded because then the fraction is 7(0)/0 and is undefined. The numerator can be zero whenever it wants, so x=7 ...
*May 15, 2016*

**Algebra**

well, A is true, but so is C. So, the answer is D. If you had solved the quadratic you would have found both solutions 7x+84 = -x^2+40x-6
*May 15, 2016*

**Math**

44lb * 1kg/2.2lb * 14day * 30mg/(kg-day) = 8400mg
*May 15, 2016*

**maths**

give google a try. First hit explores this topic http://mathforum.org/library/drmath/view/56394.html
*May 15, 2016*

**math**

1 and 2
*May 15, 2016*

**Pre-Calc**

Sure; it's just part of the expression. So, assuming we start with n=1, the powers and denominators go up as 3,5,7,9,... So, the sequence is -x^3/3!, x^5/5!, -x^6/7!, ... though I suspect that maybe we start at n=0. But you can fix it if that's the case.
*May 15, 2016*

**Math**

1/8 - 1/9 = 1/72 That's how much of the tank gets filled in one minute with both taps open, right? But the question is poorly worded...
*May 15, 2016*

**Math**

4x^2 + x + 9 = 0 the quadratic formula will provide you with the complex roots.
*May 15, 2016*

**Math**

use the pythagorean theorem.
*May 15, 2016*

**Math**

that is very bogus notation. Try rewriting it with ^ denoting a power, as x^2 = x squared And lose the combined fractions. Use parentheses to delineate the meaning. 2/3/4 might be (2/3)/4 or 2/(3/4) which are not the same.
*May 15, 2016*

**Algebra**

C is wrong. Check your +- signs during the expansion
*May 15, 2016*

**Maths**

smallest answer will come from subtracting the largest value from the smallest. So, 0 - 7654321
*May 15, 2016*

**Prealgebra**

no idea what two-ni means, but the product of 1 2/5 and b is 1 less than 2 1/2 of b can be written as (1 2/5)b = (2 1/2)b - 1 maybe you can take it from there...
*May 15, 2016*

**calculus question ?**

You are correct in both cases. Consider f(x) = 1/x and f(x) = tan(x)
*May 14, 2016*

**math**

since xy=k, a constant, you need y such that 4y = 8*24
*May 14, 2016*

**Maths**

surely you have the formulas necessary. Just plug in your numbers.
*May 14, 2016*

**Geometry**

looks good
*May 14, 2016*

**Math**

Huh??? The only one of those answers less than 4 hours is A!
*May 14, 2016*

**Math help.**

well, plug in -x+13 for y and you get -x+13 = x^2+6x+7 x^2+7x-6 = 0 This has two solutions, but they are not listed among the choices. Check for a typo.
*May 14, 2016*

**Algebra**

t^6 + t^3 - 8 = 0 now just use the quadratic formula for t^3: t^3 = (-1±√33)/2 Now you can use de Moivre's formula to get the various cube roots of those two values.
*May 14, 2016*

**Physics**

F = ma, so a = 4 m/s^2 v = at, so 8 = 4t. t=2 s s = 1/2 at^2 = 2*4 = 8 m
*May 14, 2016*

**math**

check for a typo. There are two solutions, but they are not listed.
*May 14, 2016*

**Math**

just do them step by step -x(5x-4) (-x)(5x) + (-x)(-4) ... 5k^2(-6k^2-2k+6) (5k^2)(-6k^2) + (5k^2)(-2k) + (5k^2)(6)
*May 14, 2016*

**Algebra**

to have one root, the discriminant must be zero. That is, 4+16m = 0
*May 14, 2016*

**math (PLZ HELP ASAP)**

p = 2d p+2 = 3(a+2) d = a+5 p+2 = 3(d-5+2) = 3(p/2 - 3) p+2 = 3/2 p - 9 p/2 = 11 p = 22
*May 14, 2016*

**Math**

same as the previous question. Just plug in the values and evaluate.
*May 14, 2016*

**Math**

just plug in their values: f(x)-g(x) = (3x+5) - (-x+9) now just simplify
*May 14, 2016*

**Math calculation**

how many oz per liter? multiply that by 2.5 divide that by 2.
*May 14, 2016*

**math (pLZ HELP ASAP)**

substitute t+7 for u and you get 10t + t+7 + 26 = 5(t + t+7) 11t + 33 = 10t + 35 t = 2 so, u=9 and the number is 29 check: 29+26 = 55 = 5(2+9)
*May 14, 2016*

**math (pLZ HELP ASAP)**

u = t+7 10t+u + 26 = 5(t+u) now just crank it out.
*May 14, 2016*

**Maths**

depends on the length of the wiper blade - inner and out radius. Then a = 1/2 r^2 θ
*May 14, 2016*

**maths**

greater than 96 odd with units less than tens. 97 121 71471928373 or many many others I think you have left out some information
*May 14, 2016*

**ALGEBRA**

well, 2+6 = 8, so ...
*May 14, 2016*

**geometry**

google is your friend. Try here: https://www.math.washington.edu/~king/coursedir/m444a00/syl/class/trapezoids/Trapezoids.html
*May 14, 2016*

**Maths**

.30a + .10o = .15(a+o) .15a = .05o 3a = o so as long as there are 3 times as many oranges as apples, this will work out. check: apples: 6 of 20 oranges: 6 of 60 total: 12 of 80 = 15% 30 of 100 30 of 300 60 of 400 = 15%
*May 14, 2016*

**maths**

the same (alternate interior angles)
*May 14, 2016*

**Algebra Quadratic**

you want the solution to mx-2 = x^2 to have a zero discriminant. So, since x^2 - mx + 2 = 0 has discriminant of m^2 - 8 I guess that tells you what m is, right? Take a look at http://www.wolframalpha.com/input/?i=plot+y%3Dx^2,+y%3D%E2%88%9A8+x-2,+y%3D-%E2%88%9A8+x-2
*May 14, 2016*

**math**

actually, its speed is the same. The velocity has opposite direction.
*May 14, 2016*

**math**

same as when it left. momentum is conserved.
*May 14, 2016*

**Math**

consider Mike and Fred as one person. At the table for 7, then there are 2*11P6 ways to seat them, since the 7th seat is always taken. and 5! ways to seat the others. If they do not sit at the big table, then there are 7! ways to seat that table and 2*4! ways to seat the other...
*May 13, 2016*

**Algebra**

(x+y)/2 > 0 x+y > 0 y > -x so, y can be positive or negative, depending on x. for example x = 3 y = -2 (x+y)/2 = 1/2
*May 13, 2016*

**PLZ HELP ASAP math**

p = 2d p+2 = 3(a+2) d = a+5 Now just crank it out.
*May 13, 2016*

**Math**

A The last digit must be 0 or 5, and the 1st digit is not 0, so ending in 0: 5*4*1 ending in 5: 4*4*1 B toss out all those starting with 8 or 9.
*May 13, 2016*

**Geometry**

the middle is the average of the two ends.
*May 13, 2016*

**Geometry**

you've posted a lot of these, and all you have to do is use your formulas. We can check your answers.
*May 13, 2016*

**Geometry**

clearly the base sides and the altitude will be 18, so v = 1/3 * 18^3
*May 13, 2016*

**6th grade math**

3/9 assuming that the pairs are together, so one draw get a pair. If the socks are loose and two draws are required, things are different.
*May 13, 2016*

**Math**

you can verify your work at http://www.wolframalpha.com/input/?i=%28%283x^4%29-%282%2Fy^5%29%29^9
*May 13, 2016*

**Math**

-n = 10
*May 13, 2016*

**Math**

Jen's answer was wrong in any case, but you should have used some parentheses to make things clear. All you need is a common denominator, as all the choices show. So, do what you do with normal numeric fractions: 6/(x+2) - 1/(x+9) = 6(x+9) - 1(x+2...
*May 13, 2016*

**integration....**

sorry - you cannot do ∫√(x dx) But, you can integrate √x dx since that is just x^(1/2) dx and the power rule gives you x^(3/2) -------------- = 2/3 x^(3/2) + C 3/2
*May 13, 2016*

**Math**

works for me.
*May 13, 2016*

**Math**

well, just start listing them: 7539 -> 1 78.. -> 4P2 79.. -> 4P2 8... -> 4P3 9... -> 4P3 now add 'em up.
*May 13, 2016*

**math**

well, a 12" tile covers 1 ft^2, right?
*May 13, 2016*

**Math**

just separate the variables: dy/(y+y^3) = dx then use partial fractions to integrate then plug in y(0) = 1 to find the constant.
*May 13, 2016*

**Maths**

depends on how far away the tree is.
*May 13, 2016*

**Math**

however, given the usual sloppiness online, I suspect we have 2/3 y + 4 = 12 2/3 y = 8 y = 3/2 * 8 y = 12
*May 13, 2016*

**math**

well, for any (x,y) the transformation is (x,y) -> (-x,y)
*May 13, 2016*

**Math**

"opposite" has no special meaning in math, but assuming you mean its additive inverse, that would be 13 + 1/9
*May 12, 2016*

**Pre-Calc**

the amount left in t years is 69*(1/2)^(t/12.4) so, plug in t=75 Note that that's about 6 half-lives.
*May 12, 2016*

**Pre-Calc**

you want t where e^.05t = 2
*May 12, 2016*

**Math**

maybe 9 10 38 40 40 85 lots of other vales could be used.
*May 12, 2016*

**Geometry**

clearly the height is 12, so the area is 1/2 * 6 * 12 = 36
*May 12, 2016*

**Math, Algebra**

No need to go to powers of 3, since 81 = 9^2. (9^2)^(3x+3) = 9^(2x-2) so, 6x+6 = 2x-2 x = -2
*May 12, 2016*

**Math**

x+y = 15 3y-4x = 4 now just crank it out.
*May 12, 2016*

**Algebra**

a road that is 48 meters wide? Man, that's some highway! And, after all the data, just what is the question? The volume of concrete needed?
*May 12, 2016*

**calculus**

just expand the polynomial and integrate f(x) = x^3+4x^2+3x
*May 12, 2016*

**Differential Calculus**

sorry about z. It is really found using the law of cosines z^2 = (8/5)^2 + 1^2 - 2(8/5)cosθ where θ is the angle between the hands. I'm sure you can figure that out.
*May 12, 2016*

**Differential Calculus**

with the center of the clock at (0,0), the distance z between the tips at t minutes after 12:00 is z^2 = m^2+h^2 z dz/dt = m dm/dt + h dh/dt m = 8/5 cos(π/30 t) h = cos(π/360 t) Now just plug in the numbers at t=120
*May 12, 2016*

**Calculus**

y = lnx The distance z from the origin is thus z^2 = x^2 + (lnx)^2 2z dz/dt = 2x dx/dt + 2lnx (1/x) dx/dt z dz/dt = (x+lnx/x) dx/dt at (1,e), z = √(1+e^2), so dz/dt = (1+1/1)(2)/√(1+e^2) = 4/√(1+e^2)
*May 12, 2016*

**Math**

20 the co- in cosine means sine of the complementary angle. If cos(90-A) = cos90cosA + sin90sinA = sinA
*May 12, 2016*

**Math**

You surely mean 6^(x-y) = 4, otherwise it would be trivial. 6^(x-y) = 4 6^x / 6^y = 4 6^y = 6^x/4 y log6 = log(6^x/4) y = log(6^x/4)/log6 or, if you like, y = (x log6 - log4)/log6
*May 12, 2016*

**calculus**

384000 = 30 x^1/3 y^2/3 y^-2/3 = 1/12800 x^1/3 -2/3 y^-5/3 y' = 1/38400 x^-2/3 y' = -y/25600 (y^2/x^2)^(1/3)
*May 12, 2016*

**Math**

well, w^0 = 1, so w^-2 = 1/w^2 or, w^-2/w^0 = w^(-2-0) = w^-2 = 1/w^2
*May 12, 2016*

**math**

time = distance/speed do the divisions and then subtract to find the difference
*May 12, 2016*

**Calculus**

x/(1/4) = tanθ 4 dx/dt = sec^2θ dθ/dt now just plug in your numbers. Careful with the units.
*May 12, 2016*

**Maths**

the powers of x go like this 6*12-0, 6*11-1, 6*10-2, 6*9-3, ... = 72, 65, 58, 51, ... So, the 4th term is 12C3 (x^6)^9 (1/x)^3 = 220x^51
*May 12, 2016*

**Math/Precal**

out of the 12! possible seatings, there are 2*11! which seat them together. (Think of the two as a single unit.)
*May 12, 2016*

**Algebra**

so what? You know that .6666 = 2/3, so 26.666 = 26 + 2/3 = 80/3 but you did not divide 638 by 1.5 on the right side better yet, 40x - 12(1.5x) = 638 40x - 18x = 638 ...
*May 12, 2016*

**Algebra - Check My Work**

all correct. good job.
*May 12, 2016*

**Physics**

ummm, how long is it kept there? every 2 years it decreases by 1/2.
*May 12, 2016*

**science**

find their speeds. Then you know that KE 1/2 mv^2 so, the ratio will be 3/4 (vH/vO)^2
*May 12, 2016*

**Maths**

assuming that B is a right angle, AC = √369 If angle A is a right angle, then AC=9 if neither, there's no way to find the third side, given only the other two.
*May 12, 2016*

**Mathematics in English**

google is your friend
*May 12, 2016*

**Math**

can't quite figure the kind of shape. some kind of prism? If so, just find the area of the base and multiply by the height.
*May 12, 2016*

**Algebra**

since the bottom is just √30, multiply top and bottom by √30. You then have (4√6 √30)/(√30 √30) = 4√180/30 = 24√5/30 = 4√5/5 or, you could note that √6/√30 = √(1/5) = √5/5
*May 12, 2016*

**Math**

swap variables and solve for y x = (y+4)/(2y-5) (2y-5)x = y+4 2xy-5x = y+4 (2x-1)y = 5x+4 f^-1 = y = (5x+4)/(2x-1) I'll check one way, you can at least do the other. If we let g f^-1, then f(g) = (g+4)/(2g-5) = ((5x+4)/(2x-1) + 4)/(2(5x+4)/(2x-1) - 5) = ((13x)/(2x-1))/((13...
*May 12, 2016*

**Math**

y=kx so, y/x = k, a constant. You want x such that 6/x = -18/6
*May 12, 2016*

**Algebra**

just like any other binomial. (2√5+3√7)^2 = (2√5+3√7)(2√5+3√7) = (2√5)^2 + 2(2√5)(3√7) + (3√7)^2 = 20 + 12√35 + 63 = 83 + 12√35
*May 12, 2016*

**Math/Precal**

there are 7 letters, so there are 7P3 = 210 ways to choose 3 of them. But the two O's are indistinguishable, so there are only 7P3/2! = 105 unique words
*May 12, 2016*

**Math**

The mistake was in starting with 9n and the saying 9n^2. 9n=3(nP2) =>9n=3(n*(n-1)) =>9n=3n^2-3n =>3n^2-12n = 0 => 3n(n-4) = 0 => n = 0,4
*May 12, 2016*

**Math**

base area = 9^2 = 81 each face has area 9*18 = 162 now just multiply each area by its cost and add up the proper number of faces.
*May 12, 2016*

**Math **

A rectangular prism is 18 inches tall and has a square base whose length is 9 inches. Oliver plans to cover the top and bottom of the rectangular prism with material A, which costs 2 cents per square inch. He then plans to cover the other four faces of the prism with material ...
*May 12, 2016*

**math**

Assuming one pole has height 6 and the other has height 11, then the distance between their tops is just √(12^2+5^2) = 13 meters
*May 12, 2016*

**energy,power,wurk**

GPE = mgh it is all KE just before impact.
*May 12, 2016*

**calculus**

find the max of f(x) = x*p(x)-c(x) = x(300-x)-(20000+24x+1/2 x^2) = -3/2 x^2 + 276x - 20000 f' = -3x + 276 f'=0 at x=92 since f" < 0, that is a max.
*May 12, 2016*