x2 + x – 42 = x2 +– 42

To split the middle term, find two terms whose coefficients add to 1 and whose product is −42. The numbers 7 and −6 work: 7 + (−6) = 1 and 7 × (−6) = −42. So x² + x − 42 = x² + 7x − 6x − 42, matching “7x − 6x.”

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