We have seen the close connection between polynomial division and writing a quotient of polynomials in lowest terms after factoring the numerator. We can also show a connection between dividing one polynomial by another and factoring the first polynomial. letting
$$
f(x)=2 x^{2}+5 x-12.
$$
Complete the following sentence: If $f(a)=0,$ then $x-$ ______is a factor of $f(x)$.