Estimate 12x2 dx using left- and right-hand sums with four

Question

Question: 1. Estimate ₁∫²x² dx using left- and right-hand sums with four subdivisions. How far from the true value of the integral could your estimate be?

2. Without computing the sums, find the difference between the right- and left-hand Riemann sums if we use n = 500 subintervals to approximate

_-1∫¹ (2x³ + 4)dx