3-17. Solve the following differential equations by means of the Laplace transform. d f(t) (a) dt [dx(t) df (t) dt +5- +4(t)=eu(t) (Assume zero initial conditions.) = x(t) =2x(t)3x2(t)+us(t)x, (0)=1,x2(0)=0 (b) dt dx,(t) dt +2 d y(t) d y(t) + dy(t) +2y(t)=-eu(t) dt2 dt dt (c) d y dy dt2 (0)=-1(0)=1 y(0)=0 dt 3-18. Use MATLAB to find the Laplace transform of the functions in Prob. 3-17.