Let <i> F</i> be a field, <i>a</i> belong to  <i>F</i>, and <i>f(x)</i> belong to <i> F[x]</i>. Then <I>a</I> is a zero
of <i>f(x)</I> if and only if <i>x - a</i> is a factor of <i>f(x)</I>.