Laplace and inverse Laplace transform

Using Matlab, find x(s) and x(t) for the following differential equations: d2x dx a. x 2t2u(t) b. + x = cos(2t)u(t) c. 3 g + x cos(2t) u(t) x(O) = O; x'(O) O x(O) x'(O) 0