Question 84674
f(g(x)) = f(3x+1)

        = (3x+1)^2 +2

       = 9x^2 + 6x + 1 + 2

       = 9x^2 + 6x + 3

       = 3(3x^2 + 2x + 1)


b)  let y = 3x + 1

  Interchange x and y

   x = 3y + 1

  x - 1 = 3y

  (x-1)/3 = y

So g^-1 (x) = (x-1)/3