## Elementary Technical Mathematics

$3(x-3)(x-7)$
Factor out the common term of 3, then factor the resulting trinomial. $3x^2-30x+63=3(x^2-10x+21)$ The first term in each binomial must be x, since $x^2$ has no coefficient. The operation in each binomial must be subtraction, since the trinomial has a positive and a negative term. $-3+(-7)=-10$ and $-3\times(-7)=21$, so the other two terms are -3 and -7.