If the function f (x) defined on R + satisfies f (x) + F (y) + 2XY (XY) = f (XY) / F (x + y) for any x, y ∈ R +, then f (2)=______

If the function f (x) defined on R + satisfies f (x) + F (y) + 2XY (XY) = f (XY) / F (x + y) for any x, y ∈ R +, then f (2)=______

If the function f (x) defined on R + satisfies f (x) + F (y) + 2XY (XY) = f (XY) / F (x + y) for any x, y ∈ R +, then f (2)=____
Let x = y = 2, then 2F (2) + 32 = f (4) / F (4) = 1, so f (2) = - 31 / 2