Question

done

Answer 1

This is using the fundamental theorem of calculus. It says something like, that if you find this function F(x) such that F'(x) = f(x) then the value of the integral, as written in the link, is F(5) - F(0).

Answer 2

And you know that the value of the integral is 9, so....

Answer 3

Yeah, that's right. That's the idea.

Answer 4

That's alright. It's a question designed to get you thinking about the fundamental theorem of calculus a little bit...