hmmm. According to the auto grader, the answer for mine is:

4*e^(-1*4*t) + (1 + 4*4 + 1)*t*e^(-1*4*t) - (t-3)*e^(-1*4*(t - 3))*step(t - 3)

 

a very simple solution can be obtained if u add & subtract 4 in the numerator
leaving the coeff. 4 alone.Then u can reduce the equation to standard form

 

a very simple solution can be obtained if u add & subtract 4 in the numerator
leaving the coeff. 4 alone.Then u can reduce the equation to standard form

Can you be more specific? What you wrote doesn't make any sense to me.