Mathematics Homework Help

I’m stuck on a Differential Equations question and need an explanation.

Solve these for me please and show the explanations. Thank you so much.

1- Use the method of undetermined coefficients to find one solution of: y”- y’- y = 2e^(2t)

y(t) = ?

2- Find the solution of y”+7y’ = 392 sin(7t) + 392 cos(7t)

with y(0) = 2 and y'(0) = 9

y = ?