SOLUTION: 3^-3x = 81 I started here by taking the log of both sides to solve for x. My final answer ended up 4/-3, or -1.333. This was marked wrong. Any insight?

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Question 1088599: 3^-3x = 81
I started here by taking the log of both sides to solve for x. My final answer ended up 4/-3, or -1.333. This was marked wrong. Any insight?
Found 2 solutions by addingup, MathTherapy:
Answer by addingup(3677)   (Show Source): You can put this solution on YOUR website!
3^(-3x) = 81
log(3^(-3x)) = log(81)
Since the logarithm of a number raised to a power is the power times the logarithm of the number:
((-3)x)(log(3)) = log(81)
(-3)x = log(81)/log(3)
(-3)x = log_3(81) = 4
x = 4/-3 = -1.3333
Well, I'm afraid I haven't been of any help since I got the same answer you got and obviously your teacher is looking for a different answer. But I have solved the problem correctly, so whoever is telling you that this is the wrong answer is, in my view, making a mistake. S/he needs to work the problem so s/he can see that the answer book they have is incorrect. Good luck.

Answer by MathTherapy(10556)   (Show Source): You can put this solution on YOUR website!

3^-3x = 81
I started here by taking the log of both sides to solve for x. My final answer ended up 4/-3, or -1.333. This was marked wrong. Any insight?
YOU NEED TO USE PARENTHESES! Is it: ? 

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