Which of the following functions are written using function notation? g(x) = 5x + 2 y = 1 x h = x2 r(x) = x f/x = x5 - 3 b(x) = 1 2 x3 p/x = -7x k(x) = - 3 x + 1 y = mx + b fx = -x3 + 4