b 14 [f(x)dx = lim E f(c,)Ax, , is always true for any function f, where [a, b] is X-00 a 1=1 partitioned into {x1, X2, ..., XJ, with Ax, = X, - X,_1, and c, is in [x,, x_1]. 15 f(x)=|x| is not integrable over [-1, 1] because it is not differentiable at x=0