A real valued function f x satisfies the function equation f x y f x f y ndash f a x f a y where a i...........

A real-valued function f(x) satisfies the function equation f(x-y) =f(x)f(y) –f(a-x) f(a+y) where a is a given constant and f(0) =1, f(2a-x) is equal to:

f(a)+f(a-x)

f(-x)