Chapter 4.7, Problem 12P

In each of Problems 10 through 13, use the method of variation of parameters to find a particular solution of the given differential equation. Then check your answer by using the method of undetermined coefficients.

$y\text{'}\text{'}+2y\text{'}+y=3e^{-t}$     (Compare with Problem 9 in Section 4.5.)

9. $y\text{'}\text{'}+2y\text{'}+y=3e^{-t}$     (Compare with Problem 12 in Section 4.7.)