Wednesday

January 18, 2017
Total # Posts: 47,946

**Maths**

50 cm = 1/2 meter so, yes.

*November 24, 2016*

**Math grade 5, two-part problem**

a/b = 3/4 (a+72)/b = 3/1 4a = 3b a+72 = 3b 4a = a+72 a = 24 so, b=32 check: 24+72 = 96 = 3*32

*November 24, 2016*

**mathematics**

1.25^t = 2

*November 24, 2016*

**i want help maths cal**

r=4 r sin? = 4 see similar examples here: http://tutorial.math.lamar.edu/Classes/CalcIII/SphericalCoords.aspx

*November 24, 2016*

**help me calculus**

This is just a pair of cones: z^2 = 4r^2 If ? is the angle from the z-axis, then the cone is just since z=2r, tan? = 1/2

*November 24, 2016*

**Algebra**

no solutions x+y = 2 x+y = 3 many solutions x+y = 2 2x+2y = 4 You can rearrange terms to get different forms For the table, just pick 5 values for x, and calculate the corresponding values for y, using your equation.

*November 24, 2016*

**Calculus - ok**

yes, you did. My bad.

*November 23, 2016*

**Calculus**

and y=0

*November 23, 2016*

**Calculus**

the slope of the secant is (1/8^6 - 1)/7 ? -1/7 f' = -6/(x+1)^7 so, you want -6/(c+1)^7 = -1/7 c ? 0.7 c is in the interval Since f is monotonically decreasing, there is no other value for c.

*November 23, 2016*

**Calculus**

let u = 3x^3 du = 9x^2 dx so you have ?[0,??] x^2 sin(3x^3) dx = 1/9 ?[0,3?] sin(u) du = 1/9 (-cos(u))[0,3?] = 1/9 (-cos3? + cos0) = 1/9 (1+1) = 2/9 so, the average value is 2/(9??)

*November 23, 2016*

**Calculus**

s(t) = t^2/15 if 0 <= t <= 90 = 90^2/15 + 3(t-90) if 90 < t <= 108 = 594 + 9(t-108) - (t-108)^2/15 if 180 < t s(t) = 0 when t=291.54

*November 23, 2016*

**Trigonometry**

the period is 4?, so f(x) = cos(x/2) since cos(u)=1 at u=0, we have f(x) = cos((x-?/2)/2) see http://www.wolframalpha.com/input/?i=cos((x-%CF%80%2F2)%2F2)+for+0+%3C%3D+x+%3C%3D+5pi Now recall that cos(x) = sin(?/2 - u)

*November 23, 2016*

**Math please explain how to do this**

just start evaluating: (x-520,000)/[(800,000+880,000)/2] = (x-520,000)/[1,680,000/2] = (x-520,000)/840,000 = x/840,000 - 26/41

*November 23, 2016*

**physics**

work = force * distance force = mg

*November 23, 2016*

**pre calculus**

|u|^2 = 1^2+7^2 does not matter what v is.

*November 23, 2016*

**Algebra 1 A**

money <= 100 cost for x gallons (16 cups/gal) = .20*16x + 2.33x = 5.53x sales: .50*16x = 8.00x profit: 2.47x

*November 23, 2016*

**pre calculus**

(u•v)(u + v) = (-1*4 + 7*(-3))<-1+4,7+(-3)> = (-25)<3,4> = <-75,100>

*November 23, 2016*

**Calculus**

f(-3) = f(3) = 0 The only horizontal tangent is at x=0.

*November 23, 2016*

**business maths**

annual interest is P((1+.06/2)^2-1) so, you need P(1.03^2-1) = 500 P = $8210.18

*November 23, 2016*

**Calculus**

f'(x) = (x^2)^2 (2x) - x^2 (1) = 2x^5-x^2 Google differentiation under the integral for several explanations. Wikipedia has a good article. This is really just the chain rule in reverse.

*November 23, 2016*

**Math**

4 1/2 = 18 * 1/4 so, 10 : 1/4 = 180 : 4 1/2

*November 23, 2016*

**Calculus - fundamental theorems**

The chain rule says that df/dx = df/du * du/dx. So, you have e^(x^3)^2 (3x^2) = 3x^2 e^(x^6) now, technically, you have to subtract f(u) at the lower limit, but since d1/dx = 0, it just goes away. wikipedia has a good article on this.

*November 23, 2016*

**Calculus - Fundamental Thm of Calc**

F' = f(x)dx/dx - f(1)d1/dx = t^3 - 0 = t^3

*November 23, 2016*

**calculus**

|<a,b>|^2 = a^2+b^2

*November 23, 2016*

**maths**

the LCM is probably 35 If the larger number is 210, then the ratio says that 5:7 = 150:210

*November 23, 2016*

**Ptofit and Loss**

with 12 oranges in a dozen, that makes them $5 each. So, ...

*November 23, 2016*

**math**

15x+9y=30 now subtract to eliminate y.

*November 23, 2016*

**vertical motion physics**

due to symmetry, the max height is reached after 5 seconds. y = vi*t - 5t^2 at t=5, v=0, so since v = vi - 10t, vi-10*5=0 vi=50 y = 50t-5t^2 y(5) = 50*5-5*25 = 125

*November 23, 2016*

**Math**

just plug in the numbers. Should not be too hard.

*November 23, 2016*

**Math**

http://www.wolframalpha.com/input/?i=%7B%7B1,3,2%7D,%7B2,-1,-3%7D,%7B5,2,1%7D%7D*%7B%7Ba%7D,%7Bb%7D,%7Bc%7D%7D+%3D+%7B%7B3%7D,%7B-8%7D,%7B9%7D%7D

*November 23, 2016*

**precalculus**

the entire circumference is 40*2? = 251.33 cm so, 227/251.33 = 0.9 of the whole circumference the angle is thus 0.9 * 2? = 1.8? radians 1.8? * 180/? = 324°

*November 22, 2016*

**science**

None. Fe contains no hydrogen.

*November 22, 2016*

**Math**

for a triangle in standard position, sinC = y/r since r is always positive, you must have y>0. That is QI and QII. Since cosC = x/r, you must have x<0, so QII You have a 7-24-25 triangle, so the terminal point of the hypotenuse lies at (-7,24). If you are new to this, ...

*November 22, 2016*

**Math**

csc? cos? = -1 1/sin? cos? = -1 cos?/sin? = -1 as with any angle, cos^2? + sin^2? = 1 In this case, cos? = -sin? tan? = -1 ? = 3?/4 or 7?/4 No idea at all? Hmmm. I cannot believe that the question was assigned, yet the material never taught!!!??? And have you never heard of ...

*November 22, 2016*

**Algebra2**

Expand the logarithmic expression. log8 a/2 My answer is log8a-log8 2

*November 22, 2016*

**maths**

clearly the scale is 1:3 So, multiply the diameter by 3.

*November 22, 2016*

**Math iniqualties and versitiles**

the first way involves distributing the 3 through the parenthesized expression. The second just illustrates the order of evaluation (inside the parens first), and has nothing to do with the distributive property.

*November 22, 2016*

**Algebra**

much better.

*November 22, 2016*

**Algebra**

nope. both wrong. What did you do? Find the vertex and the roots.

*November 22, 2016*

**Math**

actually, since you allow for 2 or more members, I'd say that all integer values can be formed using members of the set. In fact, using just {-1,0,1} will produce all integer values.

*November 22, 2016*

**Math**

all integer values from -8 to +8

*November 22, 2016*

**Math**

The curve for the line integral is just x = 9cos(t) y = 9sin(t) z = 0 Now just evaluate F.dr and integrate for t in [0,2pi]

*November 22, 2016*

**Math**

1/4 x = 28

*November 22, 2016*

**Trigonometry**

x/12 = cos40

*November 22, 2016*

**English**

1=2 3 I have never heard #3 I'd think: as opposed to "below" the mountain? 4 is ok

*November 22, 2016*

**Math**

I prefer D. No one is over 3 meters tall!

*November 22, 2016*

**MATH**

What do you do to check whether a number is rational or irrational? In your explanation, use an example of an irrational and a rational number.

*November 22, 2016*

**Algebra**

if there are breaks in the graph, the x-values at the breaks are excluded from the domain. If there is a minimum or maximum y-value, that sets the boundary on the range. Hard to believe you can't figure these, since you have the graph!

*November 22, 2016*

**Math**

0.8522727 MILES

*November 22, 2016*

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

you need another side, so since L is the included angle, I'd guess (D) since you need sides including L and M

*November 22, 2016*

**English**

all are good. recollect usually refers to a specific memory, not a general past.

*November 22, 2016*

**English**

I'd say device. It's a device with wings and engines. The whole mechanism is called an airplane.

*November 22, 2016*

**math**

it's an ellipse. x^2 + y^2/16 = 1

*November 22, 2016*

**calculus help**

y = r sin? x = r cos? r^2 sin^2? = r cos? r = cos?/sin^2? = csc? cot?

*November 22, 2016*

**maths need help**

log_9(a+3)-log_9(b) = c + (1/2) log_3(a-3)+log_3(b) =c - 1 (a+3)/b = 9^(c+1/2) (a-3)b = 3^(c-1) (a+3)/b = 3*9^c (a-3)b = 3^c/3 a+3 = 3b*3^(2c) 3(a-3)b = 3^c 3(a+3)(a-3)b = 3b*3^(3c) a^2-9 = 27^c a^2 = 9+27^c I expect you can get the rest.

*November 22, 2016*

**Maths**

well, since y=15-2x^2, just solve 3x+9(15-2x^2) = 1 18x^2 - 3x - 134 = 0 now just use the quadratic formula

*November 22, 2016*

**Math**

you sure you don't mean a^4 - 13a^2 + 36 ? let u = a^2 and try factoring u^2-13u+36 which two factors of 36 add to 13?

*November 22, 2016*

**maths**

The diagonals bisect each other, and also meet at an angle of 125°. So, the long side of the parallelogram can be found using the law of cosines. Let the parallelogram be ABCD and the center be E. AB^2 = 3^2+4^2 - 2*3*4*cos125° AB = 6.2262 Now, the altitude of triangle...

*November 22, 2016*

**maths**

(6/2)^2 * h = 2/3 (15/2)^3 h = 125/4

*November 22, 2016*

**Maths**

Hmmm. what two factors of 36 add to 13? Try factoring u^2-13u+36 and let u=x^2

*November 22, 2016*

**Calculus**

let u = cos(3x) and see what happens

*November 22, 2016*

**Calculus**

Good luck with this - an elliptic integral.

*November 22, 2016*

**Math**

well, there are 60 minutes in an hour, so just divide by 60. Hint -- it is not 56 mi/min

*November 22, 2016*

**Math**

Take a look here, and all will become clear. https://in.answers.yahoo.com/question/index?qid=20130823004513AAdmLmh

*November 21, 2016*

**Math**

If the roots are p and rp, then you have b/a = -(p+rp) c/a = p*rp see what you can do with that

*November 21, 2016*

**Physics- Equilibrant Force**

The resultant force is 71 NE So, the equilibrant force is 71 SW

*November 21, 2016*

**Physics- Accleration of a Falling Penny**

if the force increases (more upward) the the net downward force must decrease. So, (a) since F=ma

*November 21, 2016*

**algebra**

how about fixing the formatting?

*November 21, 2016*

**dav chd**

let x = w-1 x^4-4x^3+2x^2+4x+4 = (w+1)^4 - 4(w+1)^3 + 2(w+1)^2 + 4(w+1) + 4 ...

*November 21, 2016*

**Econ math/logarithms**

8 = 2^3 log8 = 3 log2 = 3*0.39 = 1.17

*November 21, 2016*

**Gauss-Jordan elimination**

fix your typo and visit http://www.gregthatcher.com/Mathematics/GaussJordan.aspx for all the details

*November 21, 2016*

**Calculus**

You know that lim sinu/u = 1 so, lim tanu/u = 1 (because lim cosu = 1) So, lim tan(7x)/x = lim (tan(7x)*7)/(7x) = 7 lim tanu/u where u7x = 7 or, using L'Hospital, lim tan(7x)/x = lim (7 sec^2(7x))/1 = 7

*November 21, 2016*

**Trig**

You know that the standard parabola x^2 = 4py has focus at (0,p) and directrix at y = -p. Your parabola has been shifted so its vertex is at (-2,6). 4p=8. So, the focus is 2 above the vertex and the directrix is 2 below the vertex.

*November 21, 2016*

**math**

Let the printed area xy=50 The total area is a = (x+2)(y+4) = (x+2)(50/x + 4) = 4x + 58 + 100/x so, find where da/dx = 0 (and x>0)

*November 21, 2016*

**math**

it is the slope of the line joining (1,f(1)) and (2,f(2)): (1,20/4) and (2,20/16) (20/16 - 20/4)/(2-1) = ?

*November 21, 2016*

**Math**

s shares at price p gives sp = 308 (s+6)(p-3) = 308 sp+6p-3s-18 = 308 308+6p-3s = 18 2p-s = 6 2p - 308/p = 6 2p^2 - 6p - 308 = 0 p^2 - 3p - 154 = 0 (p-14)(p+11) p = 14 s = 77

*November 21, 2016*

**science**

work = force * distance

*November 21, 2016*

**Math**

2,47

*November 21, 2016*

**Math algebra**

If the quicker person takes x hours, then the slower person takes 3x hours. 1/x + 1/3x = 1/4 12+4=3x x = 16/3 so, 3x = 16 hours for the slowpoke.

*November 21, 2016*

**Math**

looks good to me

*November 21, 2016*

**Chemistry 20**

Zn + CuSO4 = Cu + ZnSO4 same number of moles of each

*November 21, 2016*

**Math**

since column 1 is the one-times column, the row must be 4.

*November 21, 2016*

**Physics**

(a) v^2 = 2.5^2 + 4.5^2 (b) 2.5 (c) 4.5

*November 21, 2016*

**Maths help asap please.**

think: (a+1)^2 = a^2+2a+1

*November 21, 2016*

**math**

the + or - status does not matter. Just find the rule as usual.

*November 21, 2016*

**maths**

t = u+2 (10t+u) + (10u+t) = 88

*November 21, 2016*

**Physics**

well, 5min = 1/12 hr. Now use the hint.

*November 21, 2016*

**Algebra pt. 2**

That's better, but express them a as pair of coordinates. (12,4) not just 12 4.

*November 21, 2016*

**maths**

x+24 + 10 = 3(x+10)

*November 21, 2016*

**Algebra**

NO Take each point and double its coordinates. Stop trying to get rid of the coordinates. The problem says to come up with a new list of coordinates for the expanded diagram. (6,2) becomes (12,4)

*November 21, 2016*

**Algebra**

No, you multiply each coordinate by the scale factor: 2 That's what the scale factor is for. what can it possibly mean to multiply x-values by y-values? You are trying to convert a point into a number. Bogus...

*November 21, 2016*

**mathematics**

what? reposting after just 5 minutes?

*November 21, 2016*

**maths**

well, 6 = 72/12, so ...

*November 21, 2016*

**Mathematics**

Let the ages of France, Emma, Father be x,y,z. Then we have x = 2y x+y = z-12 z=30 So, start substituting till you can find y.

*November 21, 2016*

**Algebar**

you have a difference of two squares a^2-b^2 = (a-b)(a+b) where a = 9x^3 b = 5y^5 Now just plug and chug.

*November 21, 2016*

**math**

chain rule: (a) 4(x^2+1)^3 * 2x (b) not sure what you mean by "primitive" The extrema (max and min) can be found where 8x(x^2+1)^3 = 0

*November 21, 2016*

**maths**

22.5

*November 21, 2016*

**Math**

x-21 = 71-x

*November 21, 2016*

**motion**

Take a look at this example. It is very similar to yours. http://www.a-levelmathstutor.com/m-momimp-coeffrest.php

*November 21, 2016*

**Math, Surds @Reiny got it**

My bad. I read "diagonal" not "area"

*November 21, 2016*