Tuesday

December 6, 2016
Total # Posts: 46,892

**CALC**

google is your friend. Many of these problems have been solved before, or ones like them. www.math.umn.edu/~emanlove/2263sum11/HW%2034.pdf

*December 6, 2016*

**precalculus**

well, geez -- just look at the equations. Surely you can notice the +/- signs, axis lengths, etc.

*December 6, 2016*

**Calc**

dy/du = sec^2u du/dv = 1 + 1/v^2 dv/dx = 1/x dy/dx = dy/du * du/dv * dv/dx now just crank it out. It's just algebra from here.

*December 6, 2016*

**math**

is (2,1) supposed to end up at (-1,4)? If so, why the intermediate point? The final translation is just (x,y) -> (x-3,y+3)

*December 6, 2016*

**Science. Answer Check**

false. In a series circuit, one failure causes the whole chain to stop. Parallel means that the current flows through each light "in parallel" with the others -- the lights each get their own current. Better look at a circuit diagram again to refresh your memory.

*December 6, 2016*

**math**

Hmmm. The problem says 9 people. How do you justify your answer?

*December 6, 2016*

**Algebra**

6200 * 1.08^t = 8750 * 1.06^t (1.08/1.06)^t = 8750/6200 ...

*December 6, 2016*

**elimination**

rearrange things to a standard format: x - 2y = -7 8x + 5y = 7 multiply #1 by 8: 8x - 16y = -56 8x + 5y = 7 Now just subtract, and the x's are eliminated...

*December 6, 2016*

**math**

Nope. -5(8) = -40 Now subtract 4 Your answer is -4 -5(w-8)

*December 6, 2016*

**math**

a=7 d=3 ...

*December 6, 2016*

**Math**

If the distance is x, then we have for the area a = 15*4 = 8x

*December 6, 2016*

**Maths**

looks like 4.5 for depth, -4.5 for height

*December 6, 2016*

**math**

2?rh = 1760 ?r^2h = 12320 square the area equation, and now you have 4?^2 r^2 h^2 = 1760^2 ?r^2 h = 12320 Divide and you have 4?h = 1760^2/12320 ...

*December 6, 2016*

**Math**

Your equation just satisfies y varies directly as x. What about the rest? y = ax + b/x + c Now use the points to get 3 equations in a,b,c and solve them.

*December 6, 2016*

**Calc**

dy/dx = dy/dt / dx/dt = (3/(2?(3t+1))) / (3t^2-1) at x=1, that is (3/(2*2))/(2) = 3/8

*December 6, 2016*

**Calc**

plug in lnx for x and then use the chain rule. f(lnx) = 6(lnx)^3 - 4lnx

*December 6, 2016*

**Calculus**

The question is incomplete: smallest n for what? You can easily verify that y^(2) = -y y^(4) = y and the odd orders are plus/minus cosine.

*December 6, 2016*

**Maths**

see related questions below

*December 6, 2016*

**Math**

If the numerator is even and differs by 3 from the denominator, then the denominator is odd. (Thus, the prime 2 is ruled out.) At that point, saying that their product is even is redundant. odd primes are 3,5,7,11,13,... So, the fraction could be 2/5, 4/7, 14/11, ...

*December 6, 2016*

**G.p.**

again? ar^6 = 1/9 ar = 27 divide, and you have r^5 = 1/3^5 r = 1/3 So, a=81

*December 6, 2016*

**maths**

2*5 = 10 so its fractions terminate. Try using 3 and see what happens.

*December 6, 2016*

**Meth**

fix the typo. Then maybe we can pick an answer.

*December 6, 2016*

**harmonic progression**

since the reciprocals are in AP, yes, it is an HP.

*December 6, 2016*

**Algebra**

well just plug in t=6 into your somewhat awkward formula.

*December 6, 2016*

**G.p.**

is that 2^(2-b) or 2^2 - b?

*December 6, 2016*

**math**

x + x+2 = x+4 + 16

*December 6, 2016*

**g.p.**

ar^3/ar^11 = 1/r^8 = 1/2^8 so, r = 2 I expect you can take it from there...

*December 6, 2016*

**Calculus**

I'd say no. It's just an exponential function. No way any logs can creep in there.

*December 6, 2016*

**Calculus**

well, geez - did you try it to check? f = e^(1-x) = e*e^-x f' = e*(-1)e^-x = -f

*December 6, 2016*

**Calculus**

Just using the product, quotient, and chain rules, I'd say (u'v + uv')(w) - uvw' --------------------------- w^2

*December 6, 2016*

**Calculus**

y = x + 4/x has a max at x = -2

*December 5, 2016*

**Calc**

v = x(6x)*y y = V/(6x^2) A = x*6x + 2xy + 2*6xy = 6x^2 + 14xy = 6x^2 + 14x(V/6x^2) = 6x^2 + 7V/(3x) Now just find where dA/dx = 0.

*December 5, 2016*

**Alegbra**

you have basically a = bR^3 R^3 = a/b = 15000/(4pi/3) = 45000/4pi = 11250/pi R = ?(11250/pi)

*December 5, 2016*

**Pre Calculus**

just solve for t when h(t) = 0.

*December 5, 2016*

**Math**

A better question might be how did you get yours? Did you draw a diagram? since sin(30) = 1/2, the pole is 15/2 meters tall. A 45-45-90 triangle has equal legs, so base of the 2nd wire is 15/2 meters from the pole. I'll leave the rest to you. The Pythagorean Theorem should...

*December 5, 2016*

**Math**

That's not what I get. I get (15/2)(?3-1) How did you get your answer (which is not exact, by the way)?

*December 5, 2016*

**Algebra**

the maximum profit is at the vertex of the parabola. As you know, the vertex of the parabola ax^2+bx+c is at x = -b/2a y = (b^2-4ac)/4a So, for -10x^2+100x-210 the vertex is at (5,40) Since x=5, the price is 10-x = 5 as well.

*December 5, 2016*

**math**

If their numbers are x,y,z, then we know x/y = 2/7 x/z = 2/3 z = y-8 x+y+z = 24

*December 5, 2016*

**Science**

Recall that F = ma Now just use your numbers.

*December 5, 2016*

**Algebra**

Recall that the parabola x^2 = 4py has its vertex at (0,0) and its directrix at y = -p.

*December 5, 2016*

**Algebra**

If we set the vertex at (0,0) then the curve goes through (30,30) y = 1/30 x^2 x^2 = 30y Since the parabola x^2 = 4py has its focus at y=p, 4p=30 and the mic should be 15/2 inches up from the vertex.

*December 5, 2016*

**maths**

well, it lost 12%, so it retains 88% of its initial value. So, ...

*December 5, 2016*

**Calculus**

f(lnx) = 6(lnx)^3 - 4lnx Now you can use the chain rule.

*December 5, 2016*

**maths**

google is your friend. You could have solved this problem in one minute: https://www.algebra.com/algebra/homework/Circles/Circles.faq.question.308572.html

*December 5, 2016*

**Math**

32 hr * 6 lawns/8hr = 24 lawns

*December 5, 2016*

**Math**

1/10 + 1/B = 1/6

*December 5, 2016*

**Math**

check to see how much salt is coming in and going out. Since pure water contains no salt, and the 5 gallons leaving contain 5/100 of the salt present, we have ds/dt = 5/100 * 0 - 5/100 s ds/dt = -1/20 s ds/s = -1/20 dt s = c*e^(-t/20) Since s(0) = 10, s = 10*e^-(t/20) so, let...

*December 5, 2016*

**Math**

see the related questions below. They should help you set up and solve your differential equation. If you get stuck, come back with what you have done so far.

*December 5, 2016*

**Calculus**

you are correct: http://www.wolframalpha.com/input/?i=plot+y%3Dx%5E3%2B1%2F4,+y%3D3x%2F4,+-1%3C%3Dx%3C%3D1

*December 5, 2016*

**Math**

x^3+2y^3 = 5xy 3x^2 + 6y^2 y' = 5y + 5xy' y'(6y^2-5x) = 5y-3x^2 y' = (5y-3x^2)/(6y^2-5x) y" = [(5y'-6x)(6y^2-5x)-(5y-3x^2)(12yy'-5)]/(6y^2-5x)^2 2xy(54x^3-270xy+108y^3+125) -------------------------------------- ...

*December 5, 2016*

**parametrics**

Your parametric equations are right. The second quadrant is pi/2 <= t <= pi

*December 5, 2016*

**Math**

At height h, h/4 = tan? 1/4 dh/dt = sec^2? d?/dt So, plug in your numbers and find dh/dt

*December 5, 2016*

**Geometry**

Assuming the three points lie on a single line, then since the slope is constant, (5-2)/(4-1) = (2-0)/(1-x) x = -1 Note that x changes by the same amount as y between points. Since y changed by -2, from 2 to 0, x changed by -2, from 1 to -1.

*December 5, 2016*

**precalculus**

x^2/a^2 + y^2/b^2 = 1 The semi-axis lengths are a and b. Naturally, the larger is the major. If it's a, the ellipse lies horizontally. If it's b, the ellipse stands up, because the major axis is vertical.

*December 5, 2016*

**geometry**

since PB is the bisector, the other two angles are equal. x+2 = 2x-6 solve for x, and then you can find your angle.

*December 5, 2016*

**Calc**

f(x)=2sinx-sin2x f(7pi) = 0 f(8pi) = 0 f(x) is continuous. So, it satisfies the MVT. In fact, it satisfies Rolle's Theorem. (f(8pi)-f(7pi))/(8pi-7pi) = 0 f'(x) = 2cosx - 2cos(2x) = 2cosx - 2(2cos^2x-1) = -4cos^2x + 2cosx + 2 = -2(2cos^2x - cosx - 1) = -2(2cosx+1)(cosx-...

*December 5, 2016*

**Calc**

see your other post

*December 5, 2016*

**precalculus**

replace y by (y-k) and x by (x-h) Better review your text where it talks about translation of functions.

*December 5, 2016*

**precalculus**

you know what y=ax^2 is, right? Now shift it by (h,k)

*December 5, 2016*

**Math**

You can always multiply by 1 without changing things. A conversion factor is just a way of writing 1 so that units cancel as desired. Suppose you want to convert lbs to kg. You know that 2.2lb = 1kg So, 2.2lb/1kg = 1 1kg/2.2lb = 1 So, if you want to convert kg to lbs, you can ...

*December 5, 2016*

**Math**

P(1st=0) = 1/6 P(2nd=0) = 1/6 P(either) = 1/3

*December 5, 2016*

**Math**

The same as the probability that either of them is zero.

*December 5, 2016*

**precalculus**

(a) and (b) are equivalent, since you can write them as (y-k) = a(x-h)^2 (y-k) = 4p(x-h)^2 You have (b) and (c) right. I thought we already went over this...

*December 5, 2016*

**Mathematics**

No, you must check. You already have the alleged answers!

*December 5, 2016*

**Maths**

you are correct, but it seems a bit convoluted. Still, if it helps you sort out the quantities, good job.

*December 5, 2016*

**precalculus**

I don't see any questions. Just statements of the properties. If you understant (x-h)^2 = 4p(y-k) then I don't see what the problem is with (y-k)^2 = 4p(x-k) Go to wolframalpha.com and type in some functions and see what happens. For example, http://www.wolframalpha....

*December 5, 2016*

**Calculus 1**

x dx/dt + y dy/dt = 0 Now just plug in your numbers.

*December 5, 2016*

**Math**

the unit price per egg is 48/30. Add 15% profit and multiply by 100: (48/30)*1.15*100 = Rs 184

*December 5, 2016*

**Calc**

correct. Having trouble visualizing that, where h tries to change from concave down to up at x = -1, but fails, and stays concave down? h(x) = x^6/30 + 3x^5/20 + x^4/12 - x^3/2 - x^2 It's a strange bird. You can see it straightening out, then staying concave down until x=1...

*December 5, 2016*

**Calc**

As you can see, g'(1)=0 twice. So, g' is negative on both sides. That means the function is falling, comes to a momentary stop, and then keeps on falling. (Think of y=x^3, y'=3x^2. y'=0, but is rising on both sides.) g(1) is neither a max nor a min. Since g'...

*December 5, 2016*

**Maths**

a+4d = 3(a+d) a+11d = 2(a+5d)+1 Solve for a and d, then T16 = a+15d

*December 5, 2016*

**algebra, mathematics**

x + y = 33 y - 2x = 15

*December 5, 2016*

**Silmultaneous Equations**

I'll just use x and y, giving ?(5/8-(?5/8))x+cos(43°)y = 0 0.58778x + 0.73135y = 0 1/4(1+?5)x+sin(43°)y-2g=0 0.80902x + 0.68200y = 19.6 Now just solve by your favorite method (I suggest substitution).

*December 5, 2016*

**Silmultaneous Equations**

what do the LH and RH mean?

*December 5, 2016*

**Math**

no, it's not

*December 5, 2016*

**math115**

Your equation shows him just getting 1/2 time for extra hours. For time and a half, you need P(t) = 880 + 22*1.5(t-40) = 880 + 33(t-40)

*December 5, 2016*

**math**

what, no possible ideas for this? Let x be the number. Then four times a number is 4x now work on the rest of the clues. Just put them into math symbols.

*December 5, 2016*

**fundamental programming**

x=5 while (x?0) read x

*December 5, 2016*

**Math grade 10**

the slope of AB is 1/4 So, you want a line with slope -4 that contains C(1,4). Use the point-slope form, and you have y-4 = -4(x-1)

*December 5, 2016*

**Math - Coordinate Geometry**

you have a slope (4) and an intercept (-3), so try the slope-intercept form: y = 4x-3

*December 5, 2016*

**math**

.25x + .60(90-x) = .53*90

*December 4, 2016*

**Math**

So, I guess you did not read the web page I suggested ... r = ed/(1+e sin?) r=4/(-2-6sin?) r = -2/(1+3sin?) so, e=3 and d=2/3 in x-y coordinates, that is (y-3/4)^2 - x^2/8 = 1/16 http://www.wolframalpha.com/input/?i=hyperbola+(y-3%2F4)%5E2+-+x%5E2%2F8+%3D+1%2F16 You can see ...

*December 4, 2016*

**Algebra**

one way is just plain substitution. You know that y = 5x-3, so use that in the other equation: y = -3x+5 5x-3 = -3x+5 8x = 8 x = 1 Now, y = 5x-3 = 5-3 = 2 substituting for x will also work, but then you have fractions to work with, since x = (y+3)/5 or (5-y)/3

*December 4, 2016*

**Algebra**

The + on the left means it's a circle or ellipse. The differing coefficients for x^2 and y^2 means it's an ellipse. In standard form, that is just x^2/25 + y^2/9 = 1

*December 4, 2016*

**Math**

You say Suppose m?438° what does that mean? Hmm. Maybe you mean m?4 = 38° Not sure what the figure looks like, but corresponding angles are congruent. Check for adjacent angles or alternate/vertical angles. It's kind of hard to answer a question about a diagram ...

*December 4, 2016*

**PreCalc**

every 10s the amount drops by 1/2, so m(t) = 5 * 2^(-t/10)

*December 4, 2016*

**PreCalc**

clearly, n(t) = 1500*(12000/1500)^t = 1500*8^t = 1500 e^(2.07944t)

*December 4, 2016*

**Math**

suppose I said 8 = r/4 How would you do that? Multiply by the denominator, right? So, r = Td Now divide by T to get d all alone: d = r/T

*December 4, 2016*

**Math**

We are talking about 7*24+1 = 169 hours. So, the clock loses 84.5 minutes in that time. ...

*December 4, 2016*

**Math**

depends on the coins.

*December 4, 2016*

**Math grade 10**

Just verify that they intersect at (3,3)

*December 4, 2016*

**Maths**

sorry. that's ?x-2?

*December 4, 2016*

**Maths**

y = 0.50 for x <= 2 0.50 + 0.10(x-2) for x > 2 technically, it is a step function, so y = 0.50 + 0.10⌈x-1⌉ for x > 2

*December 4, 2016*

**Math**

Just plug in your numbers. (a) H = 27.5 + 2.24*20 (d) 68 = 24+2.32F (e) as femurs lengthen, men grow more slowly

*December 4, 2016*

**Maths**

If the number is ab, then a = 2b 10a+b - 18 = 10b+a

*December 4, 2016*

**Maths**

a+b+c = 1000 a = b+120 b = c+110 b+120 + b + c = 1000 c+110+120 + c+110 + c = 1000 3c+340 = 1000 3c = 660 ...

*December 4, 2016*

**Calculus**

If the man's shadow has length s, then using similar triangles, when the man is x meters from the building, s/15 = 1.69/(15-x) s = 25.35/(15-x) ds/dt = 25.25/(15-x)^2 dx/dt Now plug in your numbers

*December 4, 2016*

**Calculus**

x^2+y^2 = 225 x dx/dt + y dy/dt = 0 now just plug in your numbers and solve for dy/dt

*December 4, 2016*

**math**

naturally, that would be 0.40 * 20, right?

*December 4, 2016*