To determine which logarithmic expression is undefined, we need to recall the properties of logarithms:
- The logarithm of a non-positive number (zero or negative) is undefined.
- Logarithms are defined for positive real numbers only.
Now, let's evaluate each expression:
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\( \log_3(-9) \): This is undefined because the argument (−9) is negative.
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\( \log_{3.1}(9.61) \): This is defined because both the base (3.1) and the argument (9.61) are positive.
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\( \log_3(9) \): This is defined because both the base (3) and the argument (9) are positive.
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\( \log_{1.32}(2.8561) \): This is defined because the base (1.32) is positive and greater than 1, and the argument (2.8561) is also positive.
Based on this analysis, the expression that is undefined is:
\( \log_3(-9) \)