Factor \({x}^{2}+10x+21\).
Ask: Which two numbers add up to \(10\) and multiply to \(21\)?
Rewrite the expression using the above.
\[(x+3)(x+7)\]
Solve for \(x\).
Ask: When will \((x+3)(x+7)\) equal zero?
When \(x+3=0\) or \(x+7=0\)
Solve each of the 2 equations above.
\[x=-3,-7\]
