Mathematics - 8 November 2007

Can you help me with this: Solve the differential eq:

2(dy/dx) - 4xy = 5x ; (y=10 when x=1)

This is what i have so far:

dy/dx - 2xy = 5/2x

so, e^(-x^2)(dy/dx) - 2xye^(-x^2) = 5/2xe^(-x^2)

Dx (e^(-x^2)y) = 5/2xe^(-x^2)

I'm stuck. I know the next step involves substitution but I don't know how to proceed.

2007-11-08 13:13:55 · 4 answers · asked by Anonymous

-2
_____
√a^3

Is what in simpliest form. I got this can you check if this is correct:

-2
___
a^2

IF not explain the steps you used. Thanks

2007-11-08 13:07:41 · 3 answers · asked by Grid 7

use pascal's triangle

2007-11-08 13:01:58 · 2 answers · asked by Anonymous

Birthday paradox- in a random gathering of 23 people, there is a 50% chance that two people will have the same birthday.

2007-11-08 12:43:17 · 4 answers · asked by Kaylight 1

There's two problems. Oh and these are "Explain your thinking" problems.

1. How do you tell if 2 ratios form a proportion or not?

2. What is the percent proportion? Tell how you can use it.

Thank you so much for those who are will to help me! Oh, one more thing, these are 7th grader questions so bare with me. XP

2007-11-08 12:33:53 · 1 answers · asked by Anonymous

A solid is formed by adjoining two hemispheres to the ends of a right circular cylinder. The total volume of the solid is 12 cubic centimeters. Find the radius of the cylinder that produces minimum surface area.

Here's what I did:
1. drew the solid. It looks like a pill.
2. labelled the radius of the cylinder "r" and the height "h".
3. Used the volume equation to solve for h in terms of r. I got h = (12 - 4/3*pi*r^3) / pi*r^2.
4. Plugged that value of h into the equation of the solid's surface area and simplified.
5. Differentiate but the equation looks messy. I don't know how I can set that equation equal to zero and solve for r.

Or if there's a better method, please feel free to teach me that.

2007-11-08 12:28:20 · 2 answers · asked by coconutty beanz xD 4

2007-11-08 12:26:50 · 4 answers · asked by Anonymous

Solve for C please.

Using factorization

2007-11-08 12:18:31 · 3 answers · asked by Anonymous

Solving Quadratics

x(squared)+5x=0

2007-11-08 12:18:19 · 5 answers · asked by Rosey 2

2007-11-08 12:15:43 · 4 answers · asked by Jeff J 1

Why is (cosθ1.cosθ2 - sinθ1.sinθ2) equal to cos(θ1+θ2)?

And why is (sinθ1.cosθ2 + cosθ1.sinθ2) equal to sin(θ1+θ2)?

Note: I've seen this in a chapter about complex numbers.

2007-11-08 12:12:41 · 4 answers · asked by thehill88o 1

2007-11-08 12:12:15 · 5 answers · asked by niceymath 1

tell if the problems are prime, or the two numbers that go with them...
please im only in eight grade and i missed half this classs for orhtodonsits

x^2+39x+140
z^2+30z+160
u^2 +77u+360
x^2-98x+2001

2007-11-08 12:10:11 · 2 answers · asked by sdffasdfasfvasfewaaerqwer 1

Find three consecutive even integers such that three times the smaller and twice the middle number is equal to six times the larger.
First=
Second=
Third=
(I have to come up with algebraic expressions and solve for the aswer) Word problems are my weakness.

2007-11-08 12:09:40 · 2 answers · asked by Mandy 2

how do you find the derivative of this logarithmic function?

y= x ^ (1/ lnx)

2007-11-08 12:07:56 · 4 answers · asked by Anonymous

2007-11-08 12:06:51 · 2 answers · asked by Anonymous

the denominator of a fraction is four less than twice the nemerator.if three is added to both the numerator and denominator, the new fraction is equal to two thirds. find the original fraction. only an algebraic solution please!

2007-11-08 12:03:00 · 9 answers · asked by Anonymous

This is for Calculus AB or BC students only.
Please give the steps too.

2007-11-08 11:51:30 · 4 answers · asked by singer4jc108 2

f(x)=Ix2-3xI. Find f'(1)

The equation of the line tangent to y=tan2(3x) at x=p/4 is:

At what point on the curve x3-y2+x2=0 is the tangent line vertical?

If y2-2xy=21, then dy/dx at the point (2, -3) is:

2007-11-08 11:37:54 · 3 answers · asked by nyMark 2

Prove the following identity:

(1+sinx+cosx)/(1-sinx+cosx) = (1+sinx)/(cosx)

2007-11-08 11:22:17 · 2 answers · asked by Anonymous

Pick any number and double it. Add 56 to this result. Divide the sum by 2. Subtract the original number you picked.

2007-11-08 11:21:52 · 2 answers · asked by Anonymous

2007-11-08 11:18:09 · 6 answers · asked by Anonymous

If a quadratic formula x^2+bx+c has exactly 1 solution (r), then find b/c....i will be picking best answer... :)

2007-11-08 11:17:56 · 4 answers · asked by Anonymous

Please explain

2007-11-08 11:08:40 · 1 answers · asked by Bobby S 3

I've never been taught, and my math teacher is totally useless. I can determine the horizontal and vertical translations and if there's a reflection on the x-axis, but I can't figure out a way to determine the vertical stretch of a parabola.

Example:
A parabola with a vertex of (-1,-4) intercepts the x-axis at (-3,0) and (1,0).
Using this function:
f(x) = RxVS(x-HT)^2+VT
I need to come up with the equation of the graph. So far I have this:
f(x) = VS(x+1)-4

How would I get the vertical stretch?

2007-11-08 10:50:56 · 3 answers · asked by Anonymous

Hi! I understand how to solve it logically, but is there a way to solve it mathematically?

A function of f is periodic with period 3/4.
if f(1)=3 and f(17/12)=-2,
find f(2/3)

Thanks in advance

2007-11-08 10:50:54 · 2 answers · asked by Anonymous

Let f(x) = e^x / (8+(e^x))

then f'(x) = 8e^x / ((8+(e^x))^2)

In what intervals is f increasing and decreasing ?

And what are the local max and min (if they exist) ?

2007-11-08 10:48:28 · 1 answers · asked by Anonymous

F(t) = 4.5e^t

2007-11-08 10:48:14 · 3 answers · asked by nghlife 1

I mean i know the mathmatical way but how could i put it in my own words and make it much simpler. thanks

2007-11-08 10:48:03 · 1 answers · asked by need help 2

ok i know a triangle can't have two right angles but can you please explain? thanks alot!

2007-11-08 10:46:14 · 8 answers · asked by Anonymous