The function f (x) is known to satisfy f (a + b) = f (a) + F (b) - 6 for any real number a, B ∈ R. when a > 0, f (a)

The function f (x) is known to satisfy f (a + b) = f (a) + F (b) - 6 for any real number a, B ∈ R. when a > 0, f (a)

(1) Let a = - 2, B = 0
We have f (- 2) = f (- 2) + F (0) - 6,
So f (0) = 6
Let a = 2, B = - 2
f(0)=f(2)+f(-2)-6,
So f (2) = 0
(2) Let X1 > x2,
f(X1)=f(X1-X2)+f(X2)-6
f(X1)-f(X2)=f(X1-X2)-6