F (x) = {4-x, if x is less than or equal to 0 {f (x-1) - f (X-2), if x is greater than 0, then f (3)=

F (x) = {4-x, if x is less than or equal to 0 {f (x-1) - f (X-2), if x is greater than 0, then f (3)=

According to x > 0, f (x) = f (x-1) - (X-2) has
f(2)=f(1)-f(0)
So f (3) = f (2) - f (1) = [f (1) - f (0)] - f (1) = - f (0)
=-4