Riemann Sum value

Question

Find the value V of the Riemann sum V=n∑k=1 f(C_k)Δx_k for the function f(x)=x2+2 using the partition P = { 1, 3, 5, 8 }, where ck is the left endpoints of the partition.

Answer 1

V = f(1)(3-1) + f(3)(5-3) + f(5)(8-5) = (3)(2) + (11)(2) + (27)(3)