Let f (x) = 2x + 3, G (x + 3) = f (x), find the expression of G (x), please tell me quickly, thank you

Let f (x) = 2x + 3, G (x + 3) = f (x), find the expression of G (x), please tell me quickly, thank you


Solution 2x + 3 = 2 (x + 3) - 3 = g (x + 3)
g(x)=2x-3