The even function f (x) defined on R satisfies that for any x1, X2 belongs to (negative infinity, 0) (x1 ≠ x2), and (x2-x1) (f (x2) - f (x1)) > 0, then when n belongs to N +, f(n+1)

The even function f (x) defined on R satisfies that for any x1, X2 belongs to (negative infinity, 0) (x1 ≠ x2), and (x2-x1) (f (x2) - f (x1)) > 0, then when n belongs to N +, f(n+1)

Let x 10 be arbitrary
So f (x) is a decreasing function
Then f (n + 2)