5. (18%) Given +3 , find the exact area A of the region under y = f (x) on the interval [1, 3] by first computing 3-1 2 where, Xi = = 1, 2, ...,n, with Ax , and then taking the limit of A(n) as n (You must show your work to get the credit) (Hint: You can use the formulae , and E i = 2 6