Write and evaluate a Riemann sum to determine the area $A(f,-1 ≤ x ≤ 1)$ for $f(x)$ below. Choose the number of rectangles so that your answer will be a good approximation of the area. What is interesting about the sign of your result? Use a description or sketch of the function to support your answer.

$f(x) = x^4-x^2$