Use u$-$substitution to evaluate the integral.

$($a$)\backslash$int$\_0^1$ x$^(3)($x$^(4)+3)^(2)$dx$->$u$=$x$^(4)+3$

$($b$)\backslash$int$\_0^1($x$^(3))/(\backslash$sqrt$(1+$x$^(4)))$dx