19. Show that f(x) = x' -7x +2 must equal zero on the interval [ 0 , 2 ]. (4 pts.) 20. Find the derivative, f'(x) , for each of the functions. You do not need to use the limit notation but show your work. (2 pts each.) (a) f(x) =7x -12x' +4x-3 (b) f(x) = 14 (c) f(x) = 3x(2x+3) (d) f(x) =- (e) f(x) = 8/x2 (f) f (x) = (3x-7)2