Like Prove it said the substitution is very useful here.
Because you have a definite integral you can change the integration limits by using the given substitution.
The original integration limits are in function of so the new one has to be in function of so:
So the new integration limits (in function of ) are 3 and 4.
To solve the integral use the rule:
Changing the integration limits isn't necessary, you can also hold the original integration limits, but afterwards you have to do the back-substitution then.