Let f(x) = x^3 − x on [−1, 1].
Find the true area of the shaded region using a limit of Riemann
sums, taking the sample points to be the left endpoints. Hint: to
ease the computations, you can use the fact that (a + b)^ 3 = a ^3
+ 3a^2 b + 3ab^2 + b^3 (which follows by expanding the cube).
Verify your work by evaluating the corresponding definite
integral using the FTC.