Identify base and argument: Identify the base and the argument of the logarithm.We are given the logarithm log9(31). The base is 9, and the argument is 31.
Use change of base: Use the change of base formula to rewrite the logarithm in terms of common logarithms.The change of base formula is logb(a)=log(c)(b)log(c)(a), where c is a new base we choose. We can choose base 10 for common logarithms.log9(31)=log(9)log(31)
Evaluate common logarithms: Evaluate the common logarithms.We know that log(31) is the logarithm of 31 to the base 10, and log(9) is the logarithm of 9 to the base 10. We can simplify these because 9 is 32 and 31 is 3−1.310311
Divide results: Divide the two results.Now we divide the two results from Step 3 to find the value of the original logarithm.log9(31)=2×log(3)−1×log(3)
Simplify expression: Simplify the expression.Since log(3) appears in both the numerator and the denominator, they cancel each other out.log9(31)=−21
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