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Question
Solve the following:
log 8 (x2 - 1) - log 8 (3x + 9) = 0
Sum
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Solution
log 8 (x2 - 1) - log 8 (3x + 9) = 0
⇒ `"log"_8((x^2 - 1)/(3x + 9))` = log 8 1
⇒ `(x^2 - 1)/(3x + 9)` = 1
⇒ x2 - 1 = 3x + 9
⇒ x2 - 3x - 10 = 0
⇒ x2 - 5x + 2x - 10 = 0
⇒ x (x - 5) + 2(x - 5) = 0
⇒ (x - 5)(x + 2) = 0
⇒ x = 5 or x = -2.
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