# Thread: [SOLVED] Substitution Rule (Integration)

1. ## [SOLVED] Substitution Rule (Integration)

I'm not sure about something - should my u be $(x^2+10x+26)^{-1}$ or $1/(x^2+10x+26)$ ? And do I use the general power rule after the substitution?

2. I believe you maybe able to do this using the partial fractions method rather than substitution.

3. I'd rather stick to the substitution rule if that's possible. I haven't learned about partial fractions method yet.

4. Originally Posted by Archduke01

I'm not sure about something - should my u be $(x^2+10x+26)^{-1}$ or $1/(x^2+10x+26)$ ? And do I use the general power rule after the substitution?

Try $u=x^2+10x+26$

$du=(2x+10)dx=2(x+5)dx$

5. I don't quite understand, sorry.

6. hmmmm I can't explain my reasoning but as you know the top is two times the derivative of the bottom you can say 2ln(x^2+10x+26).

7. Originally Posted by Fermatwannabe
hmmmm I can't explain my reasoning but as you know the top is two times the derivative of the bottom you can say 2ln(x^2+10x+26).
Alright thanks, I solved it.