Question

Given a function f(x) = squr(3 + 2x), on [-1,1], subdivided into 4 equally large intervals, calculate the Riemann sum SR4 = 4Ei=1 f(xi)delta(x).

my attempt at the solution:

[-1,1], a = -1 and b = 1

delta(x) = 1 - (-1)/n = 2/n

xi = a + delta(x)i
xi = -1 + 2/n(i)

so after adding them up I get

40/n^2 - 8/n

Could someone please verify if this is correct?

Thank you