Math functions problem?

Let g(x) = f(x + 2). Then:

f(x) = f((x - 2) + 2)

= g(x - 2)

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

= x^2 - 4x + 4 + 3x - 6 - 2

= x^2 - x - 4

This simply is a function which is true for all value real of x

If F(x+2)=x^2+3x-2

subsitute x=x-2 in the equation

Then f(x)=(x-2)^2+3(x-2)-2

f(x)=x^2-x+2

so f(3)=3^2-3+2=8

f(x) = (x-2)^2+3(x-2)-2 = ...