Math Is Fun Forum

ziggs

Member

Registered: 2009-02-22

Posts: 7

Diff EQ

I have 2 boundary value problems to solve. The first I think i have.

a).  y'' = 3x^2 , y(0) = 0, y(1) = 0   [ y'' being the 2nd derivative]

Integrating this twice yields y = (1/4)x^4 + Cx + D
then using the initial conditions we get y = (1/4)x^4 + (3/4)x

b). y'' - 4y = 1, y(0) = 1, y(1) = 1

From here is where I could use some guidance please. Thanks.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Diff EQ

Hi ziggs;

a) Is not correct because it doesn't fit your initial conditions.

b)
This is a second order non-homogeneous DE with a constant as the non-homogeneous term. They are generally easy to solve.
Check this:
http://en.wikibooks.org/wiki/Differenti … mogenous_1

A little way down the page is a method to get the particular solution. They used to use a chart but this is much better.

Are you sure about your initial conditions?

Last edited by bobbym (2009-09-08 17:20:50)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

ziggs

Member

Registered: 2009-02-22

Posts: 7

Re: Diff EQ

thanks much :-)