f(x) = 2x + 5, [0, 2], 4 rectangles f(x) = 9 - x, [2, 4], 6 rectangles g(x) = 2x² - x - 1, [2, 5], 6 rectangles g(x) = x² + 1, [1, 3], 8 rectangles f(x) = cos x, x., [0, 1]. 4 rectangles 2 I g(x) = sin x, [0, π], 6 rectangles