x^{2}  7x  8 =0
To solve for this you want two factors of 8 that when added together is 7 and when multiplied is 8.
Given the multiple choice we know the correct factors are 1 and 8. We also know that one of the terms must be negative, that way you'll have to numbers that multiply to 8.
So it's either 1 and 8 or 1 and 8. Since 1 + 8 = 7, We know that the correct choice is 1, 8 or B.
12/15/2013

Krystal S.
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