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Problem 8 - Entrance Test

If log₂(x–1)+log₂(x+2)=2, then x equals

Correct: A

Combine: log₂[(x–1)(x+2)]=2 → (x–1)(x+2)=4 → x²+x–2=4 → x²+x–6=0 → (x+3)(x–2)=0 → x=2 or x=–3. But x=–3 makes logs undefined, so x=2.