Let's put them all of them with denominator x.
(x3+1)(x+x4)3x
Factoring the cube first, we get
(x3+1)x3(x+1)3(x2−x+1)3x
Canceling out the denominator, we get
(x3+1)x2(x+1)3(x2−x+1)3
Expanding everything, we finally get
x14+4x11+6x8+4x5+x2
That's our final answer!
Thanks! :)