K is an infinite field, f is a nonzero polynomial, prove $\exists \alpha_1,\cdots ,\alpha_n \> \in \mathbb{K}\>s.t. f(\alpha_1,\cdots ,\alpha_n)\neq0$

Question

$\mathbb{K}$ is an infinite field,$f(x_1,\cdots,x_n)\in \mathbb{K}[x_1,\cdots,x_n]$ is a is a nonzero polynomial, prove that $\exists \alpha_1,\cdots ,\alpha_n \> \in \mathbb{K}\>s.t. f(\alpha_1,\cdots ,\alpha_n)\neq0$

I tried proof by contradiction but I still don't have a clue