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Answer: log7 21 / log7 5
I took one for the team and guessed, and got it right.
You are welcome future students.
The expression that correctly shows how to rewrite the logarithm [tex]\log_5{21}[/tex], using a logarithm of base 7, with change of base, is given as follows:
[tex]\frac{\log_7{21}}{\log_7{5}}[/tex]
How to change the base of a logarithm?
To change the base of a logarithm, a new fraction is written, in which:
- The numerator is the logarithm of the new base of the number that the previous logarithm was calculated.
- The denominator is the logarithm of the new base of the base of the previous logarithm was calculated.
In this problem, the logarithm that will be calculated is:
[tex]\log_5{21}[/tex]
Hence the number and the base of the logarithm are presented as follows:
- The number is of 21.
- The base is of 5.
With the change of the base to base 7, the numerator and the denominator of the fraction are given as follows:
- Numerator: [tex]\log_7{21}[/tex]
- Denominator: [tex]\log_7{5}[/tex]
Hence the simplified logarithm is presented as follows:
[tex]\frac{\log_7{21}}{\log_7{5}}[/tex]
Meaning that the correct option is the second option.
More can be learned about the change of base of a logarithm at https://brainly.com/question/25588990
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