[tex]\begin{gathered} -3w^2+7y-wy+21w \\ \text{ rearrange the terms so that the first two and the last two terms become factorable} \\ \text{ expressions} \\ 7y-wy+21w-3w^2 \\ \text{ In order to factor the polynomial above, independently factor the first two} \\ \text{and the last two terms} \\ y(\frac{7y}{y}-\frac{wy}{y})+3w(\frac{3\cdot7w}{3w}-\frac{3w^2}{3w}) \\ y(\frac{7\cancel{y}}{\cancel{y}}-\frac{w\cancel{y}}{\cancel{y}})+3w(\frac{\cancel{3}\cdot7\cancel{w}}{\cancel{3w}}-\frac{\cancel{3}w^{\cancel{2}}}{\cancel{3}\cancel{w}}) \\ y(7-w)+3w(7-w) \\ \text{Result: }(-w+7)(y+3w) \end{gathered}[/tex]
