Solution: f (3) > 0, and one of f(5) and f( 1) must be greater than 0.

A 1+A5 = 2A3 > 0F (x) monotonically increases on (0, positive infinity).

Whether A 1 > A5 or A5 > A 1, (f (5)+f (1)) > 0 holds.

(f (a 1)+f (a3)+f (a5)) > 0 holds.

choose one