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Which values of x satisfy x^2 - 1 = 8?

A3 only
B9 and -9
C3 and -3
D7 and -7
Answer & Solution
Correct answer: C. 3 and -3
1. Add 1 to both sides to get x^2 = 9. 2. Both 3 and -3 square to 9, so both work. 3. 3 only misses the negative root, and 9 is the value of x^2, not x. _Source: Wikipedia, Elementary algebra, Equations_
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