SOLUTION: Find all numbers for which the rational expression is not defined. Separate by comma if needed. x^2-4/x^2+4x-21

Question 424220: Find all numbers for which the rational expression is not defined. Separate by comma if needed.
x^2-4/x^2+4x-21
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Find all numbers for which the rational expression is not defined. Separate by comma if needed.
x^2-4/x^2+4x-21
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Not defined if x^2+4x-21 = 0
Factor:
x^2+7x-3x-21 = 0
x(x+7)-3(x+7) = 0
(x+7)(x-3) = 0
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Undefined when x = -7 or x = 3
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Cheers,
Stan H.
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