If f (x) satisfies f (x + 2) = x2 + 3, then f (x)=______ .

If f (x) satisfies f (x + 2) = x2 + 3, then f (x)=______ .

From F (x + 2) = x2 + 3, we get f (x + 2) = (x + 2-2) 2 + 3 = (x + 2) 2-4 (x + 2) + 7, so f (x) = x2-4x + 7. So the answer is: x2-4x + 7