log7+43log(97−563) equals which of the following?
A.
None of the others
B.
-2
C.
-4
D.
-3
E.
-5
Answer
C
Explanation
Note that (7−43)2=49+48−563=97−563.
So 97−563=(7−43)2.
Also 7−43=7+431=(7+43)−1.
Thus 97−563=(7+43)−2.
Denominator: log7+43=21log(7+43).
Numerator: log((7+43)−2)=−2log(7+43).
Ratio = 21log(7+43)−2log(7+43)=−4.
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