In exercises 17-19, find the rules of the functions fog and gof. 17. f (x) = 2x2 - x-2, g( x) = x+2 18. f ( x ) = -, g (x) = Vx x 19. f ( x ) = - g ( x) =x+2 x- 2 In exercises 20-21, verify that ( f . g) (x) = x and (go f) (x) = x 20. f (x) = 3x - 6, g(x = -*+6 3 21. f ( x) = x2 - 4x, g (x) = Vx +4+2