4. Given the following, find f(x). (a) (f + g)(x) = 2x² - 5x + 6, g(x) = x² + 8x - 7 (b) (f g)(x) = x4 + 16x² + 256, g(x) = x² + 4x + 16 (c) (fog)(x) = (3x - 2)4, g(x) = 3x - 2 (d) (gof)(x) = 18x - 25. g(x) = 6x - 7 ●​