## Elementary Technical Mathematics

$3(x+3)(x-4)$
$3x^2-3x-36\longrightarrow$ 3 is a common factor $=3(x^2-x-12)$ $=3(\ \ \ \ \ \ \ \ )(\ \ \ \ \ \ \ \ )$ $=3(x\ \ \ \ \ \ )(x\ \ \ \ \ \ )$ $=3(x+\ )(x-\ )$ The factors of -12 must have unlike signs. $=3(x+3)(x-4)$ 3 and -4 have a sum of -1 and a product of -12.