Answer
$L[ t^3 e^{-4t}]=\dfrac{6}{(s+4)^4}$
Work Step by Step
The Laplace transform of function $t^3$ is given as:
$L(t^3)=\dfrac{3 !}{s^4}$
The first shifting Theorem for $a=-4$ can be expressed as:
$L[ t^3 e^{-4t}]=\dfrac{6}{(s+4)^4}$