Sarah Jane T. answered • 09/07/12

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d^{2 }+ 2d - 8 = 0

This equation can be solved by factoring. You need to look for factors of -8 that add up to 2. (In any equation of the form x^{2} + bx + c = 0, you look for factors of c that add up to b). In this case, 4 and -2 add up to 2; therefore the factors of d^{2} + 2d - 8 are (d+4)(d-2).

(d+4)(d-2) = 0

Using the zero product rule, this equation can now be separated into two seperate equations:

d+4=0 and d-2=0

Subtract 4 from both sides of the first equation and you get d = -4. Add 2 to both sides of the second equation and you get d = 2. Therefore your solution set is {-4, 2}.