Kevin C. answered • 04/10/14

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What you want to do, is get the product of (x + a)(x + b) to equal x

^{2}+ 11x + 28.If you multiply (x + a)(x + b), this equals x

^{2}+ ax + bx + ab = x^{2}+ (a+b)x + ab.Therefore. a+b = 11, and ab = 28. What numbers multiply to equal 28 and add to equal 11?

Try 7 and 4. therefore x

^{2}+ 11x + 28 = (x + a)(x + b) = (x + 4)(x + 7).If this had been x

^{2}+ 5x - 6, I would ask what numbers multiply to equal 6 and subtract to equal 5.Try 6 and 1. Therefore x

^{2}+ 5x - 6 = (x + a)(x + b) = (x + 6)(x - 1). Note that the product gives (a + b) as-x + 6x = 5x, the middle term. Always multiply be sure the factors are correct.

I hope this helps.

Kevin