log-1/3 81 is equal to ?

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log_-1/3 81 is equal to ?

1. - 27
2. - 4
3. 4
4. 127

Correct Option: C

Let log_-1/381 = x
⇒ 81 = (-1/3)^x
⇒ 3⁴ = (-1/3)^x = 3^-x
∴ x = -4