Show that the function $<p(x), q(x)>$ = $p(−1)q(−1) + p(0)q(0) + p(1)q(1)$ defines an inner product on $P\_2(R)$

I know that an inner product has to hold three conditions, but I am not exactly sure if I use $<1 + x + x^2, 1 +x + x^2>$. Any help would be greatly appreciated.