5. (18%) Given f(x) = x2 +3 , find the exact area A of the region under y = f (x) on the interval [1, 3] by first computing A(n)= ifbcAx, where, x]. =1+iAx, z' =1,2,...,n, with Ax = % = i, and then taking the lirnit of A(n) as n 9 0. (You must show your work to get the credit) n(n +1) 9 and if : n(n+1)6(2n+1)) '21 (Hint: You can use the formulae 2i: 2 1:1