If $\log_3 x = -2$, then $x$ is equal to
Aptitude
Logarithm
Difficulty: Easy
Choose an option
-
A$-9$
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B$-6$
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C$-8$
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D$\frac{1}{9}$
Answer
Correct Answer: $\frac{1}{9}$
Explanation
Concept & Formula
To find an unknown argument in a logarithmic equation, convert the logarithm into its exponential form.
$$ \log_a b = x \implies a^x = b $$
A negative exponent indicates the reciprocal of the base raised to the positive exponent.
$$ a^{-n} = \frac{1}{a^n} $$
Step-by-Step Solution
* **Given:** The equation is $\log_3 x = -2$.
* **Calculation:** Convert this logarithmic equation to an exponential equation using the base $3$:
$$ 3^{-2} = x $$
* Apply the negative exponent rule to rewrite $3^{-2}$:
$$ x = \frac{1}{3^2} $$
* Evaluate $3^2$:
$$ x = \frac{1}{9} $$
Exam Strategy & Shortcut
Whenever you see a negative result for a logarithm, it immediately means the argument is a fraction (less than $1$) if the base is greater than $1$. You know $3^2 = 9$, so the negative sign just flips it to $1/9$. You can eliminate options (a), (b), and (c) instantly because the argument of a logarithm (x) must always be positive.
Common Pitfall
A very common mistake is multiplying the base by the exponent to get $-6$, or raising it normally and then adding a negative sign to get $-9$. Always remember that a negative exponent creates a fraction, not a negative number.
Final Answer
**Therefore, the correct answer is \frac{1}{9}.**