Thursday

August 27, 2015
Total # Posts: 33,099

**Calculus**

I assume you mean ∫ cos(x)/√(sinx) dx let u^2 = sinx 2u du = cosx dx Now the integral is ∫ 2u/u du = 2∫du = 2u+c = 2√(sinx)+c
*July 23, 2015*

**Calculus**

Maybe this discussion will help. http://math.stackexchange.com/questions/359023/using-the-limit-definition-to-find-the-derivative-of-ex
*July 22, 2015*

**Algebra 1**

just count the ways the event can happen even: 11 13 15 22 24 26 31 33 35 42 44 46 51 53 55 62 64 66 So, there are 18 ways to roll an even. There are 4 ways to get a five: 14 23 32 41 So, P(even or 5) = 20/36
*July 22, 2015*

**Math grade 11 u**

h(x) = ax^2+bx+c h(142) = 0, because at that distance the ball hits the ground h(0) is the initial height when the ball was hit (it has not traveled any distance yet). So, 0.6 <= h(0) <= 1.5
*July 22, 2015*

**ALGEBRA**

If the truck has speed x, then the car has speed x+20 since time = distance/speed, 350/(x+20) = 350/x - 2 Now just solve for x, and figure x+20
*July 22, 2015*

**calculus**

The region bounded by y=√x y=0 x=3 has its "vertices" at (0,0), (3,0), and (3,√3) To rotate it about the line x=9, it's best to think of flat discs with holes in them. So, since the volume of a thin disc of thickness dy is πr^2 dy, and we need to...
*July 22, 2015*

**Math**

well, consider the fact that 6x^2-7x-5 = (3x-5)(2x+1) ...
*July 22, 2015*

**Mathematics**

well, consider the fact that 6x^2-7x-5 = (3x-5)(2x+1)
*July 22, 2015*

**math**

Assuming you meant 51x+24y = 75, you can divide by 3 to get 17x+8y = 25 So, 17x+8y = C will be parallel, regardless of the value of C. (except C=25) So, pick (B) because (D) is the same line as the original (obtained by multiplying through by 2/3).
*July 22, 2015*

**math**

an odd number of them must be negative. So, I pick (B)
*July 22, 2015*

**math**

do you know what a reciprocal is? If not, you cannot pick the right answer.
*July 22, 2015*

**math**

0 = -1 + 0 + 1 n + n+1 + n+2 = 3n+6 so it must be a multiple of 3.
*July 22, 2015*

**math**

XY = 1/4 AB altitude of CXY is 3/4 the altitude ABC. So, CXY has area 1/3 * 3/4 * 21 = 21/4
*July 22, 2015*

**Math Check**

(x^2+3)^2 = x^4 + 6x^2 + 9 so, x^2+3 = √(x^4+6x^2+9) But, √(x^4+6x^2+9) = (x^4+6x^2+9)^1/2 so, (x^4+6x^2+9)^1/2 = x^2+3
*July 22, 2015*

**Math Check**

yes.
*July 22, 2015*

**Algebra**

since area = width*length, w(2w-2) = 222 Now solve for w, and get the length.
*July 22, 2015*

**Algebra**

If the cork costs, c, then the bottle is c+1. So, adding them up, c + c+1 = 2 2c = 1 c = .50 cork: $0.50 bottle: $1.50
*July 22, 2015*

**chem**

Oh, yeah: 22.4L at STP, not 1L. (1*22.4)/(273*1) = (1.2*5.25)/(299n) n = 0.256 My 273 is included in the .08026 factor you inserted.
*July 22, 2015*

**chem**

Since PV=nRT, we have PV/nT = R is constant. So, use STP and your given numbers: (1*1)/(1*273) = (1.2*5.25)/((273+26)n) Just solve for n.
*July 22, 2015*

**Urgent math**

the quotient is indeed 2x^2 + 3x There is a remainder of 9. So, P(x) = (5x-7)(2x^2+3x) + 9 Not sure why your answer is marked incorrect, since you have the quotient right. Maybe you had to supply both Q and R. P(x)/(5x-7) = 2x^2+3x + 9/(5x-7)
*July 22, 2015*

**Urgent math**

as x→∞, -x^5 becomes more and more negative: it falls to the right: y→-∞ Similarly, as x→-∞, -x^5 rises to the left: y→∞ Since x^5 becomes so much greater than any lower powers of x, only the highest power needs to be considered...
*July 22, 2015*

**maths**

a+2d = 12 a+6d = 72 I think you can now easily find a and d and find other terms, right?
*July 22, 2015*

**math**

54 * 2/3
*July 22, 2015*

**Math**

Assuming that the pipes are to be straight from M to A and B (that is, the pipe does not go to some other point P and then divide), then let's add a couple more points to the diagram: P: the point on the river bank closest to A Q: the point on the river bank closest to B ...
*July 22, 2015*

**math**

See http://www.wolframalpha.com/input/?i=maclaurin+series+1%2F%281%2Bx%29
*July 22, 2015*

**math**

Since the series is x - x^2/2 + x^3/3 - x^4/4 + ... That would be ∞ ∑ (-1)^(k-1) x^k/k k=1
*July 22, 2015*

**Urgent math**

you can see all the details of long division by entering your polynomials here: http://calc101.com/webMathematica/long-divide.jsp
*July 22, 2015*

**Urgent math**

f(x) = x^2-8x+8 complete the square, by adding and subtracting 16, so things are unchanged: = x^2-8x+16 +8-16 = (x-4)^2 - 8
*July 22, 2015*

**College Alg**

You can see the steps here: http://www.emathhelp.net/calculators/algebra-1/synthetic-division-calculator/?numer=5x^5+%2B+10x^3+%2B+x+%2B+1&denom=x%2B2&steps=on But you will need to practice some of these on your own.
*July 22, 2015*

**College Alg**

You will have to do this graphically, since it's an algebra problem. There are lots of online graphing utilities. A good one is http://rechneronline.de/function-graphs/ You can set the domain and range and the grid resolution. Reading off the extrema will be easy.
*July 22, 2015*

**English**

(A) is the right idea: What unusual recipes it has! (B) could be expressed somewhat unusually as How unusual are its recipes!
*July 22, 2015*

**Math**

If I parse things correctly, we have πz^2rh = 2(.064^2)πr+.064*2πr z^2πr^2 = .064*2πr πr^2h = 1567.8 I get r=7.77 h=8.27 z=0.128
*July 22, 2015*

**maths**

note from #2 that x = 21y/(2y+1) put that into #1 and you have 3*21y/(2y+1) + 14y = 5y*21y/(2y+1) 63y + 14y(2y+1) = 105y^2 77y^2-77y = 0 77y(y-1) = 0 Now you have two solutions for y. Use them to get associated solutions for x.
*July 22, 2015*

**math**

There is an excellent G-J calculator here: http://www.gregthatcher.com/Mathematics/GaussJordan.aspx You can set the size of the matrix and enter the coefficients. Then it will show all the intermediate steps of the solution.
*July 22, 2015*

**Urgent math**

f(x) = 450+95x f^-1(x) = (x-450)/95 and so on
*July 22, 2015*

**College Algebra**

y = x^2+11x for inverse, switch names and solve for y: x = y^2+11y y^2+11y-x = 0 y = (-11±√(121+4x))/2 with the original domain restricted to x >= -11/2, that means y = -11/2 + √(121+4x)/2 or, consider that y = x^2+11x = (x+11/2)^2 - 121/4 restricting the...
*July 22, 2015*

**College Algebra**

x 5x 5x+9 (5x+9)^5 inverse: x = (5y+9)^5 5y+9 = x^(1/5) 5y = x^(1/5)-9 y = (x^(1/5)-9)/5
*July 22, 2015*

**Math**

1/4 * 2/3 = 2/12 = 1/6
*July 22, 2015*

**Finite Math**

well, A^5 = A^4 * A So, A = A^5 * (A^4)^-1 (A^4)^-1 = 5 -4 4 -3 So, A = 4 -5 * 5 -4 5 -6 4 -3 = 0 -1 1 -2
*July 21, 2015*

**Math**

4*5*6 = 120 = 5^3-5 -6 * -5 * -4 = -120 = -5^3 + 5 I suspect a typo in the problem.
*July 21, 2015*

**Math**

There are only 3 ways to get 3 or less: 1,1 1,2 2,1 So, there are 33 ways to get more than 3.
*July 21, 2015*

**math**

53 is a prime, so it cannot appear in any factorial less than 53! I don't see how v can be anything other than 52, but that's not one of the choices. Hmmmm...
*July 21, 2015*

**Algebra**

that would be just how much g changed: g(9) - g(-6) just plug in the values for t and do the math.
*July 21, 2015*

**MATH- URGENT!**

If it wasn't urgent at 1:55, how come it was at 1:59? Not everyone is continuously monitoring the queue, so don't bother to cry URGENT! when posting a problem. We help with solutions because it's fun for us, and we like to help. Stamping your foot and shouting ...
*July 21, 2015*

**math**

if there are x footballs, then the rest (29-x) are basketballs. So, just add up the costs: 40x + 30(29-x) = 1000
*July 21, 2015*

**calculus**

well, you know that the surface has two circular ends, and a curved lateral surface. If you unroll the cylinder, the curved surface is just a rectangle as wide as the circumference of the cylinder (2πr) and height h. So, its area is 2πrh. Add that to the two circles ...
*July 21, 2015*

**math**

y = 5 - x + 2e^x sin3x y' = 2e^x sin3x + 6e^x cos3x - 1 y" = 12e^xcos3x - 16e^x sin3x 2y' = 4e^x sin3x + 12e^x cos3x - 2 y" = -16e^x sin3x + 12e^x cos3x 2y'-y" = 20e^x sin3x - 2 10y = 50 - 10x + 20e^x sin3x 2y'-y"-10y = -52+10x or, y"-...
*July 21, 2015*

**ALGEBRA**

If the faster pipe takes x minutes, then we have 1/x + 1/(x+10) = 1/12 x = 20 So, the pipes take 20 and 30 minutes, respectively.
*July 21, 2015*

**URGENT MATH!!**

How much of the job gets done in one hour by each person? Robert: 1/12 Dennis: 1/10 Vince: 1/9 So, in 2 hours, Dennis and Vince can do 2/10 + 2/9 = 19/45 of the job That leaves 26/45 for Robert to do. At his rate of 1/12 per hour, it will take him (26/45)/(1/12) = 6.933 hours ...
*July 21, 2015*

**math**

this should help 1/4 = 3/12 1/3 = 4/12
*July 21, 2015*

**algebra**

Let x = quantity of trouser material y = quantity of shirt material Then we are told that y/3 = x/2 or, y = 3x/2 cost of shirts: 50y cost of trousers: 90x sales of shirts: 1.12(50y) sales of trousers: 1.10(90x) total sales: 1.12(50y) + 1.10(90x) = 36600 Since 3y=2x, that means...
*July 21, 2015*

**English grammar**

I disagree. "Expensive" is an adjective, it can only be modified by an adverb. In this case, "too." The infinitive phrase is an appositive. There is no predicate noun; there is a predicate adjective (expensive) The basic sentence is It is expensive. The ...
*July 21, 2015*

**Algebra**

when does g(x)=20? When x=2 So, g^-1(20) = 2 Note that g(-10) = 20 as well, but that does not matter, since we have restricted our domain to x >= -4.
*July 21, 2015*

**College Alg**

consider the parabola y=36-x^2 Its vertex is at (0,6) So, restricting the domain to 0<=x<=6 means we only want the right branch of the function. SO, the inverse function is found the usual way, by switching variables and solving for y: x = 36-y^2 y^2 = 36-x y = ±...
*July 21, 2015*

**Algebra**

well, you surely know that revenue=price*quantity. That means R(x) = x(0.28-0.000002x) C(x) = 0.087x-0.0000005x^2 P(x) = R(x)-C(x)
*July 21, 2015*

**physics**

You want the ball to land 19.6m from the wall. So, how long does it take to fall 19.6m? That would be 2 seconds. So, what horizontal speed does it take to travel 19.6m in 2s?
*July 20, 2015*

**Algebra**

the average rate of change from x=2 to x=2+h is [f(x+h)-f(x)]/h = (4(x+h)^2-4x^2)/h = (4x^2+8xh+4h^2-4x^2)/h = (8xh+4h^2)/h = 8x+4h The net change is just f(x+h)-f(x) = 8xh+4h^2 At x=2, the net change is 16h+4h^2 and the average change is 16+4h
*July 20, 2015*

**College Algebra**

you need x when g(x) = 55 x^2+6x=55 x^2+6x-55 = 0 (x+11)(x-5) = 0 Since the domain is x >= -3, that means that g^-1(55) = 5 Note that specifying that x >= -3 means we have chosen only one branch of the parabola, whose vertex is at (-3,-9). Since g(x) = x^2+6x, x = -3 &...
*July 20, 2015*

**Elementary statistics**

you want Z such that P(Z>z) = 0.75 That means that Z >= -.674 .674*4.5 = 3.033 So, you want a score of at least 78-3.033 = 74.967 The 1st quartile ends at a score of 75% You can play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
*July 20, 2015*

**Elementary Statistics**

.33 = .39-.06 = .39 - .04*1.5 so, that is 1.5 std below the mean. Now consult your Z table and find that P(Z > -1.5) = .9332 .9332*500 = 466.6
*July 20, 2015*

**Math**

Its length is 3 feet longer than its width. so, that would be x+3
*July 20, 2015*

**Chemistry**

40cm^3 * (1dm/10cm)^3 * .03mol/dm^3 = 0.0012 mol KOH Each mole of H2SO4 needs 2 moles of KOH to be neutralized. That means you had .0006 mol H2SO4 .0006mol/25cm^3 * 1000cm^3/L = 0.24mol/L = 0.24M H2SO4
*July 20, 2015*

**Algebra1**

It stays where it is. The vertex is at x=8, so a(x-8)^2 is always zero at x=8. The vertex stays at (8,9).
*July 20, 2015*

**algebra 1**

well, x^2-y^2 = (x-y)(x+y) That should help.
*July 20, 2015*

**Algebra1**

consider (x+2)^2 It is never negative, and is a minimum of zero when x = -2. So, (x+2)^2+7 has its minimum of 7 when x = -2. Read the choices carefully...
*July 20, 2015*

**math**

You have a 1/100 chance to win a $200 prize. So, your expected winnings are $2. Not much of a return on a $5 ticket. Still, it's for a worthy cause, right? . . .
*July 20, 2015*

**Algebra**

f^-1(x) = e^x g(x) = f^-1(x-2) So, reflect f(x) around the line y=x, and then shift it 2 to the right. In the graphs at http://www.wolframalpha.com/input/?i=plot+y%3Dln%28x%29%2C+y%3De^%28x-2%29%2C+y%3Dx%2C+y%3De^x you can see that f(x) is the blue curve the green curve is f ...
*July 20, 2015*

**Algebra1**

If a point (x,y) is on a graph of a function f, it means that y=f(x). That is true for both s and t in this case.
*July 20, 2015*

**Algebra1**

looks like it to me
*July 20, 2015*

**Algebra**

an even function has f(-x) = f(x) So, there are always two x's for each y. Consequently, there can be no inverse, since there will be two y's for the same value of x.
*July 20, 2015*

**Algebra1**

you are correct.
*July 20, 2015*

**Algebra1**

check to see whether 7 = (7/5)(5) what do you think?
*July 20, 2015*

**Algebra1**

well, check to see whether 9*9 + 5*5 = 0 doesn't look like it to me.
*July 20, 2015*

**math**

(7*12)(5*12)
*July 20, 2015*

**math**

6*3^2 = 54 Since the length is multiplied by 3, and the width is multiplied by 3, the area is multiplied by 9.
*July 20, 2015*

**math**

since each dimension is scaled, the area becomes (15/2.5)(25/2.5)
*July 20, 2015*

**math**

actually, since we're talking area, the new area is (1.5*7)(4*7) = ?
*July 20, 2015*

**math**

surely by now you have derived the desired equation of motion. h(t) = 7 + 85t - 16t^2 you know the max height is achieved at t = 85/32. So, is h at least 200 at that time? And why mention a speed of 150 ft/s if the upward velocity is only 85 ft/s? Do we need to assume an angle...
*July 19, 2015*

**Geometry**

the area of the base will be multiplied by 4, since it will be changed from LW to (2L)(2W) = 4LW So, apply that to finding the new volume.
*July 19, 2015*

**@ Damon**

I started reading your solution with trepidation. When I saw that we came up with the same solution, i breathed a huge sigh of relief!
*July 19, 2015*

**physics(kinematics)**

a = -8 v = -8t+c1 x = -4t^2 + c1*t + c2 x(4)=20, so -64 + 4c1 + c2 = 20 when v=16, -8t+c1=16, or t = (c1-16)/8 at that time, x=4, so -4((c1-16)/8)^2 + c1(c1-16)/8 + c2 = 4 Solve those two equations for c1 and c2, and you get c1 = 32 c2 = -44 That means that a = -8 v = -8t+32 x...
*July 19, 2015*

**Math (Finite)**

There are 15C2 ways to choose the couples. That uses up 4 people, leaving 26 individuals to make up the other 3 places on the committee. So, you have 15C2 * 26C3 = 105 * 2600 = 273,000 ways
*July 19, 2015*

**Math**

" means inches, not some weird "double prime." So, 6'3" = six feet, 3 inches, or 6.25 ft) Since the scale is constant, (3/8 ")/(1 ft) = x"/(6.25 ft) Now just solve for x: (3/8 ")/(1 ft)*(25/4 ft) = 75/32 "
*July 18, 2015*

**Nice Save, Damon.**

!!
*July 18, 2015*

**Algebra**

sometimes answer keys have errors. As far as I can see, Damon is right. 4 tests of 90 score a total of 360 points. The other test must be at least 50 to achieve the 410 points of 5 tests averaging 82 each. If any of the other high scores is less than 90, then the 4th test must...
*July 18, 2015*

**Algebra**

Here's an idea, Mr. Al. Why don't you try something else? Or, maybe you can find a flaw in Damon's logic, and get a better answer.
*July 18, 2015*

**Math**

since cos(x) starts at a maximum, you must have -cos(x) The radius is 35, so y = -35cos(x) It starts at y=2, so the axle is at y=37: y = 37-35cos(x) The period is 53, so y = 37-35cos(2pi/53 x) now just do what you need with that.
*July 18, 2015*

**math**

f is positive, increasing, and concave up. Draw such a curve, and you can see which approximations over- and under-estimate the value.
*July 17, 2015*

**calculus**

See related questions below.
*July 17, 2015*

**calculus**

well, just plug in the given condition C-cos(pi/2) = 1 C = 1 So, y = 1-cos(x)
*July 17, 2015*

**adfaf**

hint: who did the seeing?
*July 17, 2015*

**mathematics**

boats do not sail on bearings. They sail on headings. angle XYZ is 151° So, using the law of cosines, the distance XZ is z^2 = 6^2 + 7^2 - 2*6*7*cos151° If you draw the diagram, you will be able to figure all the angles needed to find the desired bearing.
*July 17, 2015*

**maths**

60 = 2*30 62 = 2*31 So, 31*60 = 30*62 That is the number of seconds that must elapse before they beep in synch again. How many seconds is that? Then convert that to a time since 10:00.
*July 17, 2015*

**algebra**

if there were x children, then the rest (2000-x) were adults. So, just add up the money: 2x + 4(2000-x) = 6000 and do the math
*July 17, 2015*

**math**

area grows by the square of the linear scale. That is because area = length*width so, if each of length and width are 1/2 as big, the area is (1/2)(1/2) = (1/2)^2 as big. So, the model is 1/4 the area of the enlarged patio.
*July 17, 2015*

**Algebra 2**

your steps and properties look good. Not sure about your initial mention of additive inverse. That appears nowhere here. a + (-a) = 0 uses additive inverse
*July 17, 2015*

**maths**

30-19 = ? assuming that you didn't eat any in the meantime... and that's how many, not how much.
*July 17, 2015*

**math**

Best guess: $2500 Not sure just what you're asking.
*July 17, 2015*

**maths**

3+1.5*5/60 = 5/60 * x
*July 17, 2015*

**maths**

since time = distance/speed, 2/(s-1.5) = 3 * 2/(s+1.5)
*July 17, 2015*