is a real number that satisfies the following equation: . What is the value of ?
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We can rewrite lo g 4 ( x − 2 ) as
lo g 4 ( x − 2 ) = lo g 2 4 lo g 2 ( x − 2 ) = 2 1 lo g 2 ( x − 2 ) .
Since 1 = lo g 2 2 , the given equation can be rewritten as
lo g 2 ( x − 5 ) = 2 1 lo g 2 ( x − 2 ) + lo g 2 2 .
Multiplying 2 on both sides, rearranging terms, and factorizing, we have
lo g 2 ( x − 5 ) 2 lo g 2 ( x − 5 ) lo g 2 ( x − 5 ) 2 ( x − 5 ) 2 0 0 = 2 1 lo g 2 ( x − 2 ) + lo g 2 2 = lo g 2 ( x − 2 ) + lo g 2 4 = lo g 2 4 ( x − 2 ) = 4 ( x − 2 ) = x 2 − 1 4 x + 3 3 = ( x − 3 ) ( x − 1 1 ) .
Thus, x = 3 or x = 1 1 . However, x = 3 cannot be a solution because x − 5 = − 2 < 0 , and the domain of the logarithm function is positive numbers.
Therefore, x = 1 1 .