SOLUTION: In solving the equation (x + 3)(x – 3) = -8, Eric stated that the solution would be x + 3 = -8 => x = -11 or (x – 3) = -8 => x = -5 However, at least one of these solutions fai

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: In solving the equation (x + 3)(x – 3) = -8, Eric stated that the solution would be x + 3 = -8 => x = -11 or (x – 3) = -8 => x = -5 However, at least one of these solutions fai      Log On


   

Question 464012: In solving the equation (x + 3)(x – 3) = -8, Eric stated that the solution would be
x + 3 = -8 => x = -11
or
(x – 3) = -8 => x = -5
However, at least one of these solutions fails to work when substituted back into the original equation. Why is that? Please help Eric to understand better; solve the problem yourself, and explain your reasoning.
Answer by algebrahouse.com(1659) About Me  (Show Source):
You can put this solution on YOUR website!
Obviously, Eric should've used: www.algebrahouse.com

He needs to multiply the (x + 3)(x - 3) first, using the foil method.
He's thinking of if they were equal to 0.

(x + 3)(x - 3) = -8
x² - 9 = -8 {used foil method}
x² = 1 {added 1 to both sides}
x = ±1 {took the square root of both sides}

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