GMAT Practice Question: The function f is defined for all nonzero x by the equation f(x)=x-1/x If x...
Question
The function f is defined for all nonzero x by the equation f(x)=x-1/x If x is not equal to 0, which of the following equals f(1/x) ?
- f(x)
- f(-x)
- f(-1/x)
- 1/f(x)
- -1/f(x)
Topics: functions, function variable substitution
Solution
Step 1
We substitute 1/x into the definition of f.
f(1/x)=1/x-11/x
Step 2
We simplify the reciprocal of a reciprocal to the original value.
f(1/x)=1/x-x
Step 3
We factor out a negative to match the original function form.
1/x-x=-(x-1/x) =-f(x)
Step 4
We verify that f(-x) also equals this same expression.
f(-x)=-x-1/-x =-x+1/x =-(x-1/x) =-f(x)
Answer
B. f(1/x) equals f(-x)
