Thursday

January 19, 2017
Total # Posts: 47,946

**Math - good catch**

thanks. leftover from a previous attempt.

*November 30, 2016*

**Math**

The volume of a spherical cap of radius r and height h (the water depth) is v = ?/3 h^2(3r-h) = ?/3 h^2(30-h) = ?/3 (30h^2 - h^3) dv/dt = ?(20h - h^2) dh/dt Now, when is h increasing most slowly? When the water surface area is greatest (since dv/dt is constant, and dv = a*dh) ...

*November 30, 2016*

**cal**

v = 10xy dv/dt = 10(y dx/dt + x dy/dt) So, using your numbers, dv/dt = 10(8(-4) + 6(2)) = -200 looks good to me.

*November 30, 2016*

**cal**

good call. So, rather than being where f' goes negative, it is where f' starts decreasing: where f" goes negative. That is, when the graph changes from concave up to concave down. Unfortunately, this graph starts out concave down, so the growth rate is always ...

*November 30, 2016*

**cal**

well, what does diminishing returns mean? Sales decrease while numbers increase. So, you want to find t for max N.

*November 30, 2016*

**cal**

f = 4x^3-21x^2+36x-4 f' = 12x^2 - 42x + 36 = 6(2x^2-7x+6) = 6(2x-3)(x-2) f" = 24x-42 = 6(4x-7) f is concave up for x > 7/4 f is decreasing for x in (3/2,2) So, both for x in (7/4,2) f has a max at x=3/2, so it cannot be concave up there.

*November 30, 2016*

**math**

what do you mean by one of the line of ax2+2hxy+by2=0 ?? That is a conic section, unless it's degenerate. In that case, you have (ax+c)(x+d)=0 ad+c = 2h cd = b Now work with the slopes of the lines, using the condition that one is twice the other.

*November 30, 2016*

**Math**

You sure there are no typos? I suspect you want (sinx+siny)/(cosx+cosy) Anyway, you can get things a bit simpler by taking the tan of both sides, since tan(arctan(x)) = x also, tan(x/2) = (1-cosx)/sinx

*November 30, 2016*

**Math Logs**

raise both sides as powers of 4, and you have, since 4^log_4(u) = u x+5 = 64(x-2) 63x = 133 x = 19/9

*November 29, 2016*

**math**

you want P where Pe^(.065*4) = 3000

*November 29, 2016*

**precalculus**

since (0,3) and (2,3) have the same y-value, the vertex is at x=1. So, (1,4) is the vertex, and we have y = a(x-1)^2 + 4 At x=0, a(1)+4 = 3 a = -1 y = -(x-1)^2 + 4 = -x^2+2x+3

*November 29, 2016*

**precalculus**

If you have to ask such a general question, you must not have read the relevant section in your text. So, you can start here: https://en.wikipedia.org/wiki/Row_echelon_form

*November 29, 2016*

**precalculus**

I get 2/x - 1/(x-1) + 2/(x-1)^2 what do you get?

*November 29, 2016*

**algebra**

m = (-5-(-10))/(-2-(-9)) = 5/7

*November 29, 2016*

**Calc**

what's the comma for? anyway, d/du arcsec(u) = 1/(x?(1-x^2)) the ?(x^2-4) I'm sure you can handle.

*November 29, 2016*

**Finite Math**

If there are x and y of A and B, then the constraints are 3x+4y <= 1000 6a+3b <= 22*60 The profit function is p(x,y) = 2.00x + 1.50y When you figure out the question you want to answer, this should help.

*November 29, 2016*

**MATH PLZ HELP**

After all the time you've spent posting this problem, don't you have any ideas? There just aren't that many ways to add at most three numbers to get 4: 1+1+2 1+2+1 2+1+1 ... Consider that she might have missed one or two throws.

*November 29, 2016*

**Math**

If the number is ab, then a.b = (a+b)/2 That is, a + b/10 = (a+b)/2 10a+b = 5a+5b 5a=4b Given the one-digit values of a and b, the number must be 45

*November 29, 2016*

**math**

so, for the 1st problem, x-2 = -2 8 = 2^3, so 2=8^(1/3) 4 = 2^2 so, 2^2 = (8^(1/3))^2 = 8^(2/3) That means 2/x = 2/3 and x=3

*November 29, 2016*

**math**

Font garbling, but (1/4)^(-2) = 16

*November 29, 2016*

**math**

27 = 3^3, so 3^(2x?1)= 1/(27^x) 3^(2x?1)= 1/3^(3x) 3^(2x-1) = 3^(-3x) 2x-1 = -3x 5x = 1 x = 1/5 25=5^2, so 5^(3x?8)·5^(4x) = 25^(2x) 5^(3x?8)·5^(4x) = 5^(4x) 3x-8+4x = 4x x = 8/3

*November 29, 2016*

**6th grade math**

(6 3/4)/6 = 1 3/24 = 1 1/8

*November 29, 2016*

**Math**

If you can do 5/6 and 3/4, then you can do 5/8. Just use a common denominator of 24 instead of 12.

*November 29, 2016*

**math**

true, 60+60=120, but there were 150 oranges.

*November 29, 2016*

**Math**

c + 5c = 24 solve for c, then get r, and then r-c

*November 29, 2016*

**maths**

clearly, 150/6 heaps so, how much profit per heap?

*November 29, 2016*

**Pre-calc**

as you know, sin(kx) and cos(kx) have period 2pi/k tan(kx) has period pi/k sin^2(x) = (1-cos(2x))/2 use a similar trick to find the period of tan^2(x) Looks like you need to review the basic info on trig functions.

*November 29, 2016*

**Math**

2*9 + 4*9 = (2+4)*9

*November 29, 2016*

**Math**

since the denominator is never zero, there is no vertical asymptote. as x gets huge, the fraction becomes tiny, so y=0 is the horizontal asymptote.

*November 29, 2016*

**Math**

well how many divisors of 24 are at least 4?

*November 29, 2016*

**Correcting Math**

65*1.07 + 65*.20 = ? Better try again. How did you arrive at your answer?

*November 29, 2016*

**pre calc**

see the post just below yours.

*November 29, 2016*

**pre calc**

don't forget your Algebra I! (2sin?+1)(sin?-1) = 0 now you can use your trig...

*November 29, 2016*

**Linear Algebra**

This is easiest with vectors, as discussed here: http://math.stackexchange.com/questions/371649/distance-of-a-3d-point-from-the-parametric-form-of-a-line Using the distance formula and calculus is a bit more involved.

*November 29, 2016*

**Math**

y = -3 x = 7 r = ?(9+49) = ?58 Now recall that sin? = y/r cos? = x/r tan? = y/x

*November 29, 2016*

**Algebra2**

8^3x=60 rewrite using the rules for exponents

*November 29, 2016*

**math**

3 * 1/6 = 3/6 = 1/2

*November 29, 2016*

**pre calculus**

see all the details here: http://www.gregthatcher.com/Mathematics/GaussJordan.aspx

*November 29, 2016*

**Pre-Calculus**

the larger of a and b is the major axis. In this case, the ellipse is vertically oriented. Think about it. When (x-2)=0, (y-4)=4 When (y-4)=0, (x-2)=3

*November 29, 2016*

**maths**

r = 1 - r cos? r(1+cos?) = 1 r = 1/(1+cos?) You should recognize this as a parabola. Now for the conversion. r = 1 - r cos? r^2 = (1 - r cos?)^2 x^2+y^2 = 1 - 2x + x^2 y^2 = 1-2x

*November 29, 2016*

**Mathmatics Asap Please!!!!!**

1+3+3 = 7 245/7 = 35 So, multiply the ratios by 35 to see what you need for 245kg of concrete: 35:105:105 Looks like there's enough for the mix.

*November 29, 2016*

**Math**

(12*71 + 92)/13 = 72 8/13 Note that 92 = 71 + 13+8

*November 29, 2016*

**Math**

Look at the changes in x and y x: up by 1 y: down by 5 so, start with y = -5x But, y(0) = -1, not 0, so y = -5x-1

*November 29, 2016*

**Math**

You want 13/2 as many cookies, so use 13/2 as much flour: (13/2) * (7 1/2) = 48 3/4 cups

*November 29, 2016*

**precalculus**

rearrange things a bit and you get 9x+18y = 17 6x+12y = 11 multiply the top by 2 and the bottom by 3 and you get 18x+36y = 34 18x+36y = 33 The two lines are parallel, so there are no solutions.

*November 29, 2016*

**precalculus**

note that if you multiply the first equation by 2, you get 4x+2y+16 So, the two equations describe the same line. Any solution to one is a solution to the other. There are infinitely many solutions.

*November 29, 2016*

**Algebra 2**

(1/6)/(1/3) = (1/6)/(2/6) = 1/2 1/6 of all the kids are scared of both.

*November 29, 2016*

**pre calculus**

You can do this. Just recall that (a) parallel lines -- same slope (b) intersecting lines -- different slopes (c) the same line -- just write it in two different ways

*November 29, 2016*

**pre calculus**

google is your friend. So is your math text.

*November 29, 2016*

**maths**

x * 6x = 5500

*November 29, 2016*

**MATH**

just multiply the dimensions. 1L = 1000 cm^3

*November 29, 2016*

**precalculus**

nope. Check the slopes. If the lines are parallel, then there is no solution.

*November 29, 2016*

**Third Grade Math**

won/total = 4/9

*November 29, 2016*

**geometry**

I see no equation. Maybe you mean r^2 cos? = cos(3?) r^2 cos? = 4cos^3(?) - 3cos? r^2 = 4cos^2? - 3 r^2 = 4(x/r)^2 - 3 x^2+y^2 = 4x^2/(x^2+y^2) - 3 (x^2+y^2)^2 + 3(x^2+y^2) - 4x^2 = 0 do with that what you will.

*November 29, 2016*

**precalculs**

just substitute y = 2x+2 into the first equation. You know a line intersects a parabola in at most two places.

*November 29, 2016*

**precalculus**

x = -y, so x^3 - 5x + x = 0 x^3-4x = 0 ...

*November 29, 2016*

**precalculus**

come on. This is Algebra I. What do you think is the answer? If nothing else, just plug in the values and see where they fit!

*November 29, 2016*

**math**

sure you do. Did you not read where it said Therefore, each factor equals 91? 3x-2 = 91 3x = 93 x = 31 It's hard to solve a problem if you don't read it!

*November 29, 2016*

**Vectors and matrices**

what's to do? Just draw the triangles. They even gave you the coordinates! Just to make sure they weren't lying, do the math: http://www.wolframalpha.com/input/?i=%7B%7B3,-1%7D,%7B5,-1%7D,%7B5,-4%7D%7D*%7B%7B1,0%7D,%7B0,-1%7D%7D

*November 29, 2016*

**algebra**

ever hear of y = mx+b It's called the "slope-intercept" form for a reason.

*November 29, 2016*

**Algebra**

well, if x is the number, what is 1/4 of the number? ...

*November 29, 2016*

**physics**

since each part has the same mass, conserving momentum is just conserving velocity: <0,8> + <-8,0> + <x,y> = 0 or, since the resultant momentum of the two known parts is NW, the 3rd part must go SE.

*November 29, 2016*

**linear equations**

reposting the same thing wastes everyone's time.

*November 29, 2016*

**math**

L = 2W 2(L+W):6L = 1:2 L+W/3L = 1/2 (2W+W)/(3*2W) = 1/2 3W/6W = 1/2 3/6 = 1/2 This is true for any value of W! I suspect the question has been mangled.

*November 29, 2016*

**Maths quadratic equation**

see related questions below

*November 29, 2016*

**Math**

google is your friend. You might want to start here: https://answers.yahoo.com/question/index?qid=20080427160136AACsLX6

*November 29, 2016*

**Math**

#1 has a typo you provide no pairs for 2,3,4,5 For #6, you know that x = y+3 So, y = x-3 I assume one of the graphs works for that. For the rest, work to isolate the variable #7 -4 = g+1 you want g all alone, so get rid of the 1 with subtraction -4-1 = g+1-1 -5 = g the others ...

*November 29, 2016*

**Math**

surely you can come up with something, at least to start with ...

*November 29, 2016*

**math**

I answered this when you were "somay" http://www.jiskha.com/display.cgi?id=1480393573

*November 29, 2016*

**Math (Calculus) (Related Rates)**

as we saw earlier, the distance z is z^2 = 1+x^2 z dz/dt = x dx/dt plugging in the numbers, z(3) = ?10, so ?10 dz/dt = 3 * 2 dz/dt = 6/?10 = 1.897 So, I guess you were right on that one. As for dz/dt when x gets large, consider that z^2 = 1+x^2 as x gets large, that is just z^...

*November 29, 2016*

**math**

This one is really quite simple, if you understand what the mean and mode are. The mode is the most frequent score. Since there are only three scores, and the mode is 11, it must occur more than any other score. That is, 11 occurs twice. Since the mean is 9, the sum of the ...

*November 28, 2016*

**math**

that would be 5

*November 28, 2016*

**math**

the slope is the rate of sales, in cars/month. So, just use the numbers given: 13cars/3months = 13/3 cars/month The slope is 13/3

*November 28, 2016*

**MATH**

flour:sugar = (3/4):(3/5) = 5:4 so, a kg of flour costs 4/5 as much as a kg of sugar. That is, 5 kg of flour costs the same as 4 kg of sugar. So, the 4 kg of sugar cost half of the $14.80. That means a kg of sugar costs $3.70

*November 28, 2016*

**math**

since 9 and 4 are both perfect squares, try (3x-2)(3x-2).

*November 28, 2016*

**Math**

hint: 15-2 = 13

*November 28, 2016*

**Math**

yes. Since both points have 4 for a y-coordinate, the line is horizontal: y = 4

*November 28, 2016*

**Math**

x would represent a number. The width is twice the height. so, 2*3(x/3+5) = 90

*November 28, 2016*

**algebra**

guess again. 2*2-1 = 3 not -1 clearly you did not test your choice.

*November 28, 2016*

**Math (Calculus) (Related Rates)**

oops. I meant find dz/dt.

*November 28, 2016*

**Math (Calculus) (Related Rates)**

at a distance x, the length of rope (z) is z^2 = x^2+1 now just find dz/dx at x=3 it should be clear how z changes when x is large.

*November 28, 2016*

**Math**

.18x = 11800 love your capitalization and punctuation and spelling. <not>

*November 28, 2016*

**maths**

x + x+4 + 3x = 44

*November 28, 2016*

**Math (please check my answer!!)**

Nope. SSA does not work.

*November 28, 2016*

**math**

well, certainly both numbers must not exceed 20. So, how many pairs x,y with x,y <= 20 fit that?

*November 28, 2016*

**Math**

suppose I asked you to find w such that 50 = 5w what would you do? Divide by 5, right? So, divide by L: W = A/L

*November 28, 2016*

**math**

T10 = a+9d = 40 S10 = 10/2 (a+40) = 265 a = 13 so, d=3 S20 = 20/2 (2*13+19*3) = 830

*November 28, 2016*

**math**

what are the perfect squares less than 12?

*November 28, 2016*

**Maths**

7sin^2x - sinx cosx - 6 = 0 divide by cos^2 to get 7tan^2x - tanx - 6sec^2x = 0 7tan^2x - tanx - 6(1+tan^2x) = 0 tan^2x - tanx - 6 = 0 there's a typo, and any solutions must exclude x where cosx=0.

*November 28, 2016*

**Math**

both do, since there are no constants involved.

*November 28, 2016*

**Math**

If z>=0, 2+z > 1 -- z > -1 2-z <= -1 -- z >= 3 If z<0, 2-z > 1 -- z < 1 2+z <= -1 -- z <= -3 graph those on the number line, and you will find your answer. Be sure to check a few values to make sure they work, especially at the boundaries.

*November 28, 2016*

**emt**

?[0,1]?[0,1] (x^2+y^2+25)^(3/2) dx dy = 130.046 This is not a trivial task, since it involves trig substitutions. Anyway, look here to find the first indefinite integral. Plug in your two y-values, giving a similar integral involving only x. http://www.wolframalpha.com/input/?...

*November 28, 2016*

**Math**

42.42

*November 28, 2016*

**Algebra**

Clearly she must add 5 liters. So, to get the concentration, .14*2 + x*5 = .34*7 ...

*November 28, 2016*

**Business Math**

Hmmm. Too bad you didn't show your work... revenue = price * quantity. breakeven is when cost = revenue, so 3600+100x+2x^2 = x(500-2x) x = 10,90 maximum profit will be at the vertex of p = r-c, halfway between the roots: x=50

*November 27, 2016*

**inverses**

I don't mean the formula. I mean, in the original problem, what was the variable x defined to be? Answer that, and you have answered your problem.

*November 27, 2016*

**inverses**

well, what does x represent?

*November 27, 2016*

**history**

This is my last question Describe some of the achievements of the Middle Kingdom of ancient Egypt.

*November 27, 2016*

**history**

What does Herodotus question about the Nile in this quote? why it has its great floods why it has no breezes blowing from it why it has its towering forests why it has its enormous length I need help bad plz. I have tried looking in my text book and everything.

*November 27, 2016*