00:01
Here we have this differential equation.
00:04
First of all, we wanna find y sub c.
00:08
We put the left -hand side equal to zero.
00:11
The characteristic equation we get looks like this.
00:14
It's got a double root, so r equals two twice.
00:22
That means that our y sub c is e to the 2x times the ax plus b, where a and b are arbitrary constants.
00:37
We wanna use undetermined coefficients.
00:39
The trial solution we would use would be y sub p is this, and substitute in and work with that.
00:48
They told us not to do it that way.
00:51
And frankly, undetermined coefficients is generally more difficult than variation of parameter, more tedious.
01:04
So for variation of parameters, what we're gonna do is we're gonna take some function f of x times e to the 2x...