Eileen is trying to test if the function f(x) = x2 + 2x + 5 is even, odd or neither. She produces the following work: f(– x) = (–x)2 + 2(–x) + 5 = x2 – 2x + 5 What conclusion can she reach? f(x) is even f(x) is odd f(x) is neither f(x) is both even and odd