Calculus
posted by Erika .
Find the integral by substitution
∫ [(16 x3)/(x4 + 5)] dx
∫[ 4 x/(√{x2 + 3})] dx
∫ 8 x2 e4 x3 +7 dx
PLEASE help with all three. i'd really appreciate it

Hints:
1. if u=x^{4}+5
du/dx
=d(x^{4}+5)/dx
=4x³
or du = 4x³ dx
2. u=√{x² + 3}
du/dx = x/√{x² + 3}
du = xdx/√{x² + 3}
3. u=?
8x²e^{4}/(x³ +7)