Find the second derivative f"(x) for f(ac) = v20ac + 9. Of" (x) = 50 (20x + 9)3/2 O f" ( I ) = - 50 (20x + 9)1/2 O f" ( ) = - 100 (20x + 9)3/2 Of" ( I ) = 50 (20x + 9)1/2 Of" ( ) = - 25 (20x + 9)3/2