F(x = 2x-5, g(x) = x²-x-6

f(x) = 2x – 5

g(x) = x² – x – 6

fog = x² – x – 6

      = (2x-5)² – (2x-5) – 6

       = 4x² – 25 – 2x + 5 – 6

       = 4x² – 2x – 26

gof = 2(x²-x-6) – 5

      = 2x² – 2x – 12 – 5

      = 2x² – 2x – 17