# Math Help - Integrating

1. ## Integrating

I don't know how to do the attached question although I do know the general formula to use.

2. Originally Posted by Stuck Man
I don't know how to do the attached question although I do know the general formula to use.
let $x=9+t$
then
$dx = dt$

3. I don't understand.

4. Originally Posted by Stuck Man
I don't understand.
Note that dt = d(t+9) or d( t + any constant) So you can now have it look like dx/x^2.

5. Originally Posted by Stuck Man
I don't know how to do the attached question although I do know the general formula to use.
Let $u = t+9$

$du = dt$

Therefore, when we sub in these values:

$\int \frac{dt}{(t+9)^2} = \frac{du}{u^2}$

That is a much simpler integral, Remember to put in the constant of integration and sub t for u in the integrated expression

6. This is more complicated that what I've learnt to do. I can see now its only the notation that confused me. I have came across this before. Instead of writing 1 on the top line dt has been placed there.