How do you factor $x²+4x-21$ ?

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Answer 1 · 2016-01-13T03:55:34

$(x+7)(x-3)$

Look for two integers whose sum is the middle coefficient, $4$ , and whose product is the final coefficient, $-21$ .

The only two integers that match this description are $7$ and $-3$ .

How do you factor x²+4x-21x²+4x-21?