Evaluate the function $f ( x ) = \log _ { 5 } x$ at $x = \frac { 1 } { 25 }$ without using a calculator.
A) $\frac { 1 } { 25 }$
B)-3
C)-1
D)25
E)-2

Question

Quizplus · Accepted Answer

Since both inputs for the function end in "_TB4590_11", we can ignore those digits and focus on the other parts of the inputs.

Notice that the first input has the same digits except for the 7th digit, which is a "6" instead of a "8". Similarly, the second input has the same digits except for the 7th digit, which is a "0" instead of a "8".

If we subtract the two 7th digits, we get:

6 - 8 = -2

Therefore, the function outputs -2, which is answer choice E.

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Evaluate the Function $f ( x ) = \log _ { 5 } x$