Tuesday

October 25, 2016
Total # Posts: 45,272

**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*

**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*

**Math**

since the parabola opens upward, the set will be all the real number line except the interval between the roots.

*October 24, 2016*

**Math**

BD divides AC in the ratio 5:13. You can use that and the law of cosines to find BD Or, knowing all the angles in ABD, use the law of sines.

*October 24, 2016*

**Please Help Math**

if you mean the complement of A, it's everything except what is in A.

*October 24, 2016*

**Math**

recall that cos(180-x) = -cos(x) and just pair up the angles. The result will be quite simple.

*October 24, 2016*

**Math**

get the angle θ between the sides using the law of cosines. area = 9.2*7.4 sinθ

*October 24, 2016*

**math**

recall the properties of the parabola y^2 = 4px Your parabola has been shifted so the vertex is at (2,-1) because 4y^2+3x=2+8y 4y^2+8y = -3x+2 4(y^2+2y+1) = -3x+2+4 4(y+1)^2 = -3x+6 = -3(x-2) (y+1)^2 = (-3/4)(x-2) Now just apply the properties of the standard parabola.

*October 24, 2016*

**Math**

We are happy to help with answers, but don't make us supply the questions as well!

*October 24, 2016*

**Math**

That's what I get.

*October 24, 2016*

**Math**

angle R = 180-58-38 = 84° Now you can use the fact that AB║PR to use corresponding angles and their supplements to find the other two angles of the trapezoid.

*October 24, 2016*

**Math**

they are in the ratio 3:4 as provided by the angle bisector theorem.

*October 24, 2016*

**maths**

Write down the sum and product of the roots of the following quadratic polynomials: (a) 3x^2 - 6x - 7 (b) 3x^2 + 6x + 7

*October 24, 2016*

**Math**

a sum

*October 24, 2016*

**physics**

vf = 11.5 m/s or 11.5 ms^-1 but not m/s^-1 = m/(1/s) = ms

*October 24, 2016*

**maths**

I assume you can apply the quadratic formula. 3x^2 + 20x - 7 The factors must be of the form (3x?1)(x?7) or (3x?7)(x?1) where the proper + or - sign must be used to get the +20x. Hint: 3*7 = 21 To solve by completing the square, proceed as in the examples in your text to get a...

*October 24, 2016*

**maths**

No I haven't

*October 24, 2016*

**Algebra 1**

all correct. Good job.

*October 24, 2016*

**Math- Please check my answer**

you are correct.

*October 24, 2016*

**Math**

use the law of cosines.

*October 24, 2016*

**Maths**

the line intersects where -x^2-x-8 = ax+1 x^2 + (a+1)x + 9 = 0 In order for there to be a single intersection, the discriminant must be zero. That is, (a+1)^2 - 36 = 0 See what you can do with that. http://www.wolframalpha.com/input/?i=plot+-x%5E2-x-8,+y%3D5x%2B1,+y%3D-7x%2B1...

*October 24, 2016*

**Maths**

the differences are 13,15,17, ...

*October 24, 2016*

**Math**

d^2 = 2s^2

*October 24, 2016*

**algebra**

a+4d = 2(a+d)+1 a+9d = 2(a+3d)+3 Now crank it out.

*October 24, 2016*

**Algebra**

These do not factor over the rationals. You need to complete the square of use the quadratic formula.

*October 23, 2016*

**Geometry**

to get the vertex angle θ, sin(θ/2) = 7/24 Once you have θ, the other two angles are equal, and they all three add up to 180.

*October 23, 2016*

**maths**

Multiples of 11 which end in 7 are 11*17 = 187 11*27 = 297 ... 11*87 = 957 So, how many are there?

*October 23, 2016*

**Math**

more frequent compounding, more money.

*October 23, 2016*

**Math**

this is not hard. Just start listing the sums: ABDM 1983: 918+318+813=2049 ... There are only 24 ways to arrange the numbers. Crank it out. I think you can eliminate all the ones where A is not 1. That makes one of the other leading letters be 1; not a likely choice.

*October 23, 2016*

**Math**

start listing the powers. You will see a pattern which makes it easy to solve this problem.

*October 23, 2016*

**math**

If he has 93 fruits, how do you come up with 6 bags of 8 fruits?

*October 23, 2016*

**Maths**

If she shoots x baskets, she scores 2x points, so she needs 94 + 2x = 16*12 and that's "in all" not "at all"

*October 23, 2016*

**Math**

review Euler's Formula for polyhedra.

*October 23, 2016*

**math**

?? The sides appear not to be integers. I guess there must be a border included in the length. √800 = 20√2 So, I guess there are 10√2 small squares across and down.

*October 23, 2016*

**Math**

Since it's going down, subtract another 40 feet: -28-40

*October 23, 2016*

**Math limits**

#1 is correct, but could be done directly. 3/x^2 -> 0 so, the limit is just 4x, which -> ∞ For #2, no tricks are involved. x^2 -> 0, so -(x^2-4)/(x^2-1) -> -(0-4)/(0-1) = -4

*October 23, 2016*

**Algebra**

(11+2w)(8+2w) = 154 You add 2w because both sides have a border. Note that 154 = 14*11

*October 23, 2016*

**math**

"increased 5 times" could mean x(+x) 5 times = 6x or x*5 = 5x I'll assume the latter, but you can fix it if you need to (5x+3)/2 = x - 0.3

*October 23, 2016*

**Math**

df/dx = 3, so df = 3 dx dx = -0.1, so ...

*October 23, 2016*

**Math**

just write what they gave you 99 ∑ 1/(k(k+1)) k=1

*October 23, 2016*

**phy101**

geez - same problem, no fixes made.

*October 23, 2016*

**N.E.U**

You want to specify all the data and try again? and that's m/s^2, not some bogus m.s.s which is meaningless.

*October 23, 2016*

**value**

why all those tedious words? It appears that you mean x+9 = 2 1/4 x On the other hand, you opaque language makes it unclear.

*October 23, 2016*

**math**

Sue is 2 mi/hr faster. So, how long to make up the 1/2 mile?

*October 23, 2016*

**Physics**

momentum (mv) is conserved. So, if v is the same, m is the same.

*October 23, 2016*

**math calculus**

If the height is y and the width is x, then a = (x+10)(300/x + 20) now find da/dx = 0 for minimum area.

*October 23, 2016*

**maths**

a common ratio indicates a g.p. (or, as nasra calls it, a go) S10 = a(r^10-1)/(r-1) a(2^10-1) = 93 a = 93/1023 and that's "the sum ... is 93"

*October 23, 2016*

**mathematics**

(2/3)x = (5/8)(31-x)

*October 23, 2016*

**Math Homework**

I assume you have some formula for seeding the teams?

*October 23, 2016*

**math**

what's the trouble? Just write down what they tell you: p = x + 4x+10 + x+3

*October 23, 2016*

**math**

∫ sin2x/√(1+cos^2x) dx u = 1+cos^2x du = -2cosx sinx ... ∫ x/[(x^2-1) ln(x^2-1)] dx u = ln(x^2-1) du = 1/(x^2-1) * 2x dx ...

*October 23, 2016*

**Algebra**

40 days and 40 nights. Now, to find Ali's number, solve 6x-30 = 78

*October 23, 2016*

**Math**

LCM(12,18) = ?

*October 23, 2016*

**Mathematics**

g^-1(x) = log3x

*October 23, 2016*

**Mathematics**

or, you know that one root is at (0,0) and since the vertex is at x=2, the other root must be at (4,0). So, y = ax(x-4) y(2) = -8, so -8 = a*2(-2) a = 2 y = 2x(x-4) This agrees with Reiny's solution above.

*October 23, 2016*

**science**

take a look here: http://physics.stackexchange.com/questions/99117/why-gravity-decreases-as-we-go-down-into-the-earth

*October 23, 2016*

**Maths**

In a square (or rhombus), the diagonals are perpendicular. Since your diagonals have a 45° angle between them, the two semi-diagonals form an isosceles triangle with vertex angle 45° and equal sides of length 3. I expect you can draw that, eh? The length is 5.544 and ...

*October 23, 2016*

**math**

what - you can't count from 20 to 30?

*October 23, 2016*