Friday

October 28, 2016
Total # Posts: 45,430

**Calculus**

If you just integrate the velocity, you wind up with the final displacement, not the distance traveled. So, to avoid subtracting backward motion, use the absolute value of the velocity: v(t) = 2t-2 distance = ∫[0,3] |2t-2| dt http://www.wolframalpha.com/input/?i=%E2%88%...

*October 26, 2016*

**Calculus**

find where dx/dt < 0

*October 26, 2016*

**math**

The others I have a hard time reading and understanding because it is written poorly maybe if you write it correctly to where I can understand I can help you with the rest.

*October 26, 2016*

**math**

2. A = 199,200

*October 26, 2016*

**math**

1. A = 205,500

*October 26, 2016*

**Calculus**

2x - 16y - 16xy' + 2yy' = 0 at (1,1) 2-16-16y'+2y' = 0 y' = 14/-14 = -1 you are correct. However, (1,1) is not on the graph. ??

*October 26, 2016*

**Math**

How can 6y-2 = 2y-2 have more than one solution? Check C. It is true for any value of x.

*October 26, 2016*

**Calculus (AC)**

y = x^(1/4) dy = 1/4 x^(-3/4) dx y(81) = 3 dx=1, so dy = 1/4 * 1/27 = 1/108 y(82) ≈ 3+1/108 = 3.00926

*October 26, 2016*

**Calc**

v = 4/3 πr^3 dv = 4πr^2 dr so, dv = 4π*200^2*.2 = 32000π cm^3 note that the dv is just the surface area times the thickness, as you'd expect for tiny thicknesses.

*October 26, 2016*

**Calc answer check**

me too

*October 26, 2016*

**Calculus (answer check)**

the propagated error (dC) is 2π*dr = 1.57 inches, not 1.57% the % error (dC/C) = .25/16 = 1.57% Since circumference is a linear function of radius, its % error cannot be greater than the % error in the radius.

*October 26, 2016*

**algebra - eh?**

I thought you just said it takes Pedro 3 days, and Juan 4 days. I suspect something has been lost in translation. Also, the notation 3 (3)/(7) is very unusual. Usually it is written as 3 3/7, unless you meant something else.

*October 26, 2016*

**Algebra**

well, the numbers are x and 3x, so ...

*October 26, 2016*

**algebra**

A: y= 110+55x B: ...

*October 26, 2016*

**Algebra 1**

Correct, but it is customary to write in descending powers: -7p^4 + p^3 + 5p + 3

*October 26, 2016*

**algebra**

I'll use a for alpha. sin(a) is not measured in degrees. sin a = 0.28 since sin^2+cos^2=1, cos a = 0.96 now just use those two values to get all the rest, using the trig function definitions.

*October 26, 2016*

**alg**

the one where each x is paired with a single y.

*October 26, 2016*

**math**

so, what do you think happens if you subtract 11 from the y value? Recall that y is the vertical axis.

*October 26, 2016*

**maths**

review Euler's Formula. see related questions below.

*October 26, 2016*

**maths**

geez, ever heard of math symbols? 2/3 ------- = 2/3 * 5/1 = 10/3 1/5

*October 26, 2016*

**maths**

well, do the math: -12/u + 4u = 9 4u^2-9u-12=0 solve for u and then consider the domain of ln x.

*October 26, 2016*

**maths**

so, did you do the substitution? 7^(2x) = u^2 the rest is just numbers, so you have a quadratic equation with a bunch of 7's floating around.

*October 26, 2016*

**math**

pick a cone pick a flavor how many choices for each? so, ...

*October 26, 2016*

**math**

s = 3c a = c-38 now add them up to 2822

*October 26, 2016*

**MATHS 2**

On the left side: cot(x+y) = (cotx*coty - 1)/(cotx + coty) = 1 cotx * coty - 1 = cotx + coty cotx * coty = 1 + cotx + coty 1 = (1 + cotx + coty)/(cotx * coty) On the right side: (cotx+1)(coty+1)/(cotx * coty) = (cotx * coty + cotx + coty + 1)/(cotx * coty) = 1 + (1 + cotx + ...

*October 26, 2016*

**Calc**

let y = ∜x dy = 1/(4∜x^3) dx y(81) = 3 let dx=1 dy = 1/(4*27) (1) = 1/108 ∜82 ≈ 3 + 1/108 = 3.009259 actually, ∜82 = 3.009216

*October 25, 2016*

**Calculus**

dr = .25 - the error in the radius a = pi r^2 da = 2pi r dr so, as you found, the variation in area is 8pi. the relative error is thus da/a = 8pi/(256pi) = 1/32 = 3.125%

*October 25, 2016*

**geometry**

think of alternate and corresponding angles. You've seen this diagram dozens of times already.

*October 25, 2016*

**Algebra 1**

(6-1.2)/(10-4)

*October 25, 2016*

**calc**

(a) z = 2/3 r^2 (b) 7r^2 = 4r sinθ r = 4/7 sinθ

*October 25, 2016*

**Calc**

this is just polar coordinates with a z. x = r cosθ y = r sinθ z = z don't forget your algebra II now that you're taking calculus.

*October 25, 2016*

**Calc**

same as polar coordinates: r^2 = x^2+y^2 tanθ = y/x

*October 25, 2016*

**Algebra 2**

It is clearly not an identity, since it is not true for all n,r. It has many solutions, since the equation describes a line. If the problem was to solve for n, then your solution is correct.

*October 25, 2016*

**Alegbra**

come on. the dimensions are x and 4x-34

*October 25, 2016*

**Algebra**

8 - (x-3)/6 + (4/5 + 703/9990)(x-3)(x-9) - (705/10000)(x-3)(x-9)(x-12) + (2586/1000000)(x-3)(x-9)(x-12)(x-24) This is from Newton's divided difference formula, because I don't see any simple pattern emerging.

*October 25, 2016*

**Math**

no idea. How long did it take? s = 1/2 at^2 All we have is the distance s.

*October 25, 2016*

**Math**

202+909 = 1111 maybe someone else can improve on that. It has been shown that every number can be written as the sum of not more than three palindromes...

*October 25, 2016*

**Math**

The unit rate is not 6 1/4 miles per kilometer. There are 0.62 miles per kilometer.

*October 25, 2016*

**Math**

well, how many times greater than 1 is 100?

*October 25, 2016*

**math**

you have two points: (0,55) and (12.5,70). The slope of that line is 15/12.5 = 1.2 y = 1.2x + 55

*October 25, 2016*

**Math, Quadratic Functions**

because when x is small, x^2 changes slowly. As x gets larger, then x^2 starts changing more rapidly. There are no sudden changes in growth rate.

*October 25, 2016*

**Math**

13/1.88 Don't be baffled by the decimal stuff. Just use easy numbers. If one Mars year were two earth years, birthdays would happen half (1/2) as often.

*October 25, 2016*

**math**

still 12

*October 25, 2016*

**math**

(5x-4)(x-4) = 448 x=12

*October 25, 2016*

**Math**

so how is 1/3 of 60 = 19.8? just as a suggestion, 1/12 of 60 = 5 Make your fractions into */12 and things get easy. Or, since only 1/3 are yellow, you could take out 2/3 of the beans with no yellows. 2/3 of 60 = 40. So, you'd have to take out 41 ti be sure of getting a ...

*October 25, 2016*

**Science: The Similarities**

no, but I'm sure google can.

*October 25, 2016*

**math**

2-3+2 = 1

*October 25, 2016*

**Math**

You lost a minus sign and made a typo. The steps should be (2^-16 x 5^10) x (5^-2/ 2^3)^4 x 2^28 (2^-16 x 5^10) x (5^-8/ 2^12) x 2^28 Now just collect powers on each base factor. 2^(-16-12+28) x 5^(10-8) = 5^2 = 25

*October 25, 2016*

**Sequence**

ar^2 = 4a ar^5 = 3(ar^3)+32 Now crank it out

*October 25, 2016*

**algebra**

no idea, but there are lots of handy calculators online. Or, you can just do the work, and we can check your answer ...

*October 25, 2016*

**Algebra 2**

well, 1/2 = 4/8, so ...

*October 25, 2016*

**Mathematics**

you need a common difference, so (4k+3)-(3k+2) = (6k-1)-(4k+3)

*October 25, 2016*

**mathematics**

38756 * .96^n = 21578

*October 25, 2016*

**Probability and Stats**

1/4 * 100 = 25

*October 25, 2016*

**Math**

699/0.40 = ?

*October 25, 2016*

**math**

and now there's no money left. What a shame.

*October 25, 2016*

**maths**

so, after the substitution, what do you have?

*October 25, 2016*

**maths**

so, did you try the hint? Time to start showing some of your work ...

*October 25, 2016*

**maths**

(i) assuming the usual sloppiness with parentheses, 3^(x+1) - 1 = 5 3*3^x = 6 3^x = 2 x = log32 (ii) 3*4^x = 4*4^(1-2x) 3*4^x = 4^2 /4^(2x) 3*4^(3x) = 16 4^(3x) = (16/3) 3x = log4(16/3) x = (1/3) log4(16/3)

*October 25, 2016*

**Math**

(12 3/8) / (3/4) = 16 1/2

*October 25, 2016*

**maths**

see below

*October 25, 2016*

**Mats Exercise 1.7**

so what? and why the backslash? Is that some new operator?

*October 25, 2016*

**maths**

check the discriminants

*October 25, 2016*

**maths**

geez - AGAIN? see the related questions below

*October 25, 2016*

**algebra**

nice try.

*October 25, 2016*

**Statistics Probability**

1/5 zero

*October 24, 2016*

**Calculus**

wait. 12 is the average slope: (f(3)-f(1))/(2-1) The average value is the integral ∫[1,3] f(x) dx ----------------- = 14 2

*October 24, 2016*

**Calculus**

I also get 12.

*October 24, 2016*

**math**

well, 23/100 = 23% so, what do you think.

*October 24, 2016*

**math**

x=-1 is the equation for the axis of symmetry y = a(x+1)^2 + k y=32 is the maximum value so a is negative y = -a(x+1)^2 + 32 3 is the x intercept This cannot be the only x-intercept, or the maximum value would be 0. So, assuming y(3) = 0, -a(4^2)+32 = 0 x = 2 y = -2(x+1)^2 + 32

*October 24, 2016*

**Math**

L1: 5x+3y=7 has slope tanθ = -5/3, so θ = -59° So, L2 needs a slope of tan(-6.6°) = -0.115 or tan(-111.4°) = 2.55

*October 24, 2016*

**MATH HELP**

you and your alternate identities need to check the related (and in fact identical) questions below. Stop posting it over and over.

*October 24, 2016*

**Mathematics**

the radius of the earth at that latitude is r = 3960 cos13° so the speed there is 2πr/24 mi/hr

*October 24, 2016*

**Maths**

oops. not so, due to h0 so, find t when h(t)=0 then use that to get v(t) at that time.

*October 24, 2016*

**Maths**

the same as when it went up.

*October 24, 2016*

**Math**

see other post.

*October 24, 2016*

**Math**

at that latitude r = 3960 * cos(13) so the speed is 2*pi*r/24 mi/hr

*October 24, 2016*

**math**

just count the possibilities on each dial, and multiply them.

*October 24, 2016*

**Algebra II**

A) note that the common difference between terms is 4. B) The common ratio between terms is 5 if I assume a typo and the first entry is -3. Otherwise, it is more complicated, and 3 terms don't give much to go on.

*October 24, 2016*

**help sir steve**

I'll let wolframalpha do it: http://www.wolframalpha.com/input/?i=arccosh(-18%5E(1%2F5)) Recall that arccosh(x) = ln(z + sqrt(z^2-1))

*October 24, 2016*

**Math**

As written, each is a function. Now, if you want to check whether y is a function of x, just check to be sure that for each x value there is a single y which satisfies the equation. hint: (-3)^2 = (+3)^2 for example

*October 24, 2016*

**True or False Math**

False a ∊ {a, b, c} c ∊ {a, b, c} {a, c} ⊂ {a, b, c}

*October 24, 2016*

**Math**

(2/9) / 2 = 2/9 * 1/2 = 2/18 = 1/9 Or, just consider that 2/2 = 1 so, 2 ninths / 2 = 1 ninth 2/7 / 2 = 1/7 2 dogs / 2 = 1 dog just half of what you start with.

*October 24, 2016*

**pre-calc.**

#1: well, f(x) = 1 for every x≠0 similarly for #2, f(x) = (x+1) for every x≠1 use your favorite online grapher to show that there is just a hole at the point in question. The limit is clear.

*October 24, 2016*

**Math HELP!**

what? You do the hard stuff, and can't rearrange terms? y = 2x-4 2x-y = 4

*October 24, 2016*

**math**

30-19 = 11 so split the difference. It will be the same as 19 - 13 1/2

*October 24, 2016*

**Math**

see your standard Z table. Here is a useful site: http://davidmlane.com/hyperstat/z_table.html

*October 24, 2016*

**calc**

uh, ... do it for each piece.

*October 24, 2016*

**Algebra**

Clearly the time working together will be less than for either working alone. 75 cannot be the answer. You need to find x such that 1/x = 1/90 + 1/60 x = 36 You have to consider how much work each one does in a minute. That is what you can add; not the required time.

*October 24, 2016*

**Five Number Summary**

have you learned how to find the mean and median? What do you get?

*October 24, 2016*

**Math**

well, the circumference is 50π

*October 24, 2016*

**geometry**

huh? If 20 is not the vertical, what is it? maybe the horizontal distance is √(30^2 - 20^2) Hard to tell from your garbled posting.

*October 24, 2016*

**physics**

√(12^2+24^2)

*October 24, 2016*

**maths**

In (a), y=4z+25 so, use that in (1) and (2). Then you just have to solve two equations. Similarly in (b), #3 gives y = 3x+2z+7 Use that in (1) and (2)

*October 24, 2016*

**Math**

If x have heard and y have not, and if r is the spread rate, r = kxy That is, r/(xy) = k is constant. So, you want r such that r/(500*300) = 20/(200*600)

*October 24, 2016*

**maths**

You and "Steve" need to get together. See related questions.

*October 24, 2016*

**maths**

all is explained in your previous posts.

*October 24, 2016*

**maths**

1a) Solve each of these questions by factorising the left hand side into a product of linear factors: (i) x^2 - 6x - 40 = 0 (ii) 3x^2 + 20x - 7 = 0 For each question in part (a), check your solutions by substituting them back in to the equation.

*October 24, 2016*

**Math**

1 - 1/2 = 1/2 1/2 - (1/2)(1/3) = 1/3 1/3 - (1/3)(1/4) = 1/4 Or, using the common denominator of 12, 12-6=6 6-2=4 4-1=3 3/12 = 1/4

*October 24, 2016*