Diff

**mladen** · May 12th 2008, 11:59 AM

need help solving this diff plz

3y´ - y = 5x

**nugiboy** · May 12th 2008, 12:16 PM

I may be wrong, but i don't think you can solve that because there is only one equation and two unknowns.

**Moo** · May 12th 2008, 12:40 PM

Originally Posted by nugiboy

I may be wrong, but i don't think you can solve that because there is only one equation and two unknowns.

It's a differential equation

y is a function of x

**nugiboy** · May 12th 2008, 12:50 PM

Originally Posted by Moo

It's a differential equation

y is a function of x

How do you do it then lol?

**mladen** · May 13th 2008, 10:06 AM

Hello again, yes I know its a diff equation but I would need some guidence and help solving it =).

thank you

**topsquark** · May 13th 2008, 11:19 AM

Originally Posted by mladen

need help solving this diff plz

3y´ - y = 5x

You can use an integrating factor:

First
$y' - \frac{1}{3}y = \frac{5}{3}x$

Then
$M(x) = e^{\int(-dx/3)} = e^{-x/3}$

So
$e^{-x/3}y' - \frac{1}{3}e^{-x/3}y = \frac{5}{3}xe^{-x/3}$

Notice that the left hand side of the equation is a "perfect derivative"
$\frac{d}{dx} \left ( e^{-x/3}y \right ) = \frac{5}{3}xe^{-x/3}$

$e^{-x/3}y = \int \frac{5}{3}xe^{-x/3}~dx$

I'll let you finish out from there.

-Dan

Thread: Diff

LinkBack

Thread Tools

Display

Diff

Similar Math Help Forum Discussions

Diff Eq. x' = t * cos(t)²

Diff eq IVP

diff eqn, sin(2x).

diff eq help

diff eq help

Search Tags