12. Find the general solution (by changing the parameters) d y - dy 4 + 5y = xe2x sin x dx y" + 6y' + 8y = e2x y" - 4y' + 4y = (x + 1)ex y"-2y' + 2y = ex (1 + sin x) a) - dx b) c) d) e) y" + y = sekx f) y" + y = kotx ex g) y"-3y' + 2y = 1+ex