integral(x^5*(sqrt(13+x^6))

Here's what I did... but its apparently wrong

1. Realized I needed to use the generalized power rule

2. set x^6+13=u

3. set 6*x^5=du

4. solved for the coeffecient. x^5*Z=du Z=6

so now I have

6*int(u^(1/2))*du

from there i got

(6*u^(3/2))/(3/2)

i plugged in the u...

(6*(x^6+13)^(3/2))/(3/2)

but this is incorrect... what'd i do wrong?