f(x+3) = x^2 + 4x + 5
x+3 = t
x = t-3
f(t) = (t-3)^2 + 4(t-3) + 5 = t^2 - 6t + 9 + 4t - 12 + 5 = t^2 - 2t + 2
f(x) = x^2 - 2x + 2
