Given, y′−4y′−12y=te4t
⇒−3y′−12y=te4t⇒y′+4y=−te4t3⇒dydt+4y=−13te4t
This is a linear form of differential equation with
I.F.=e∫4dt=e4t
Solution of the differential equation is
y(I.F.)=∫Q(I.F.)dtye4t=∫−te4t3e4tdtye4t=−13∫te8tdtye4t=−13{t∫e8t−∫ddt(t)∫e8t}ye4t=−13{te8t8−∫e8t8}ye4t=−13{te8t8−e8t64}ye4t=−e8t3{8t−164}y=−e4t192(8t−1)
So, option D is correct.