sometimes the interval would change during integration and apparently it changes when you do substitution ...are there other times where you are supposed to change it?
also let's say the original interval was rom 0 to 4 and the substitution was let u=x^2 then would the new interval be 0 to 16? I just find 16 a big number to do in our calculation if we were asked to simplify.
Hi. Substitution is the only time you change the limits of the integral. Your sample substitution is correct. Maybe 16 is a large number, but maybe the problem in this case would ask you to divide the answer by 8, say, making it much easier to handle. I wouldn't worry about simplifying too much, that's at most one mark out of the total marks for any question.