even function neither even nor odd odd function both even and odd F(X)=X2+3

We have the following definitions:
 A function is even if, for each x in the domain of f, f (- x) = f (x). The even functions have reflective symmetry through the y-axis.
 A function is odd if, for each x in the domain of f, f (- x) = - f (x). The odd functions have rotational symmetry of 180º with respect to the origin.
 We have then:
 F (-X) = (- X) 2 + 3
 Rewriting:
 F (-X) = (X) 2 + 3
 F (-X) = F (X)
 Answer:
 F (-X) = F (X)
 The function is even according to the definition: