8
6
9
7
Correct answer is C
log3x+log3(x−8)=2
log3x(x−8)=log39 since 2 = log39
log3 cancels out
⇒ x(x - 8) = 9
⇒ x2−8x=9
⇒ x2−8x−9=0
⇒ x2−9x+x−9=0
⇒ x(x - 9) + 1(x - 9) = 0
⇒ (x - 9)(x + 1) = 0
⇒ x = 9 or x = -1
Since we can't have a log of negative numbers,
∴ x = 9.
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