# How do you multiply (x + 3)(x - 7)?

 =color(blue)(x^2 - 4x -21
$\textcolor{g r e e n}{\left(x + 3\right)} . \left(x - 7\right)$
$= \textcolor{g r e e n}{\left(x\right)} . \left(x - 7\right) + \textcolor{g r e e n}{\left(3\right)} . \left(x - 7\right)$
$= {x}^{2} - 7 x + 3 x - 21$
 =color(blue)(x^2 - 4x -21