dave13
Bunuel
bmwhype2
If \(f(x) = \frac{x}{x + 1}\), what is \(f(\frac{1}{x})\) in terms of \(f(x)\)?
A. \(f(x)\)
B. \(-f(x)\)
C. \(\frac{1}{f(x)}\)
D. \(1 - f(x)\)
E. none of the above
M19-14
\(f(\frac{1}{x})= \frac{\frac{1}{x}}{\frac{1}{x} + 1} = \frac{1}{1 + x} = \frac{1 + x - x}{1 + x} = 1 - \frac{x}{1 + x} = 1 - f(x)\).
Answer: D.
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VeritasKarishma can you pls explain the logic of solution above ...mostly get wrong answers when it comes to functions
dave13How do you find the expression of \(f(\frac{1}{x})\) ? Wherever you have x in f(x), put 1/x in its place.
\(f(\frac{1}{x})= \frac{\frac{1}{x}}{\frac{1}{x} + 1} \)
Now simplify it.
\(f(\frac{1}{x}) = \frac{1}{1 + x} \)
But \(f(x) = \frac{x}{x + 1}\)
Compare the two. \(f(\frac{1}{x})\) has 1 in numerator but f(x) has x. So add and subtract x in the numerator to get
\(f(\frac{1}{x}) = \frac{1 + x - x}{1 + x} = \frac{1+x}{1 + x} - \frac{x}{1 + x} = 1 - f(x)\)
If adding and subtracting x doesn't come to mind, use the options.
You see that f(1/x) is not the same as f(x) and neither as -f(x). Then try to simplify option (D) by putting in the value of f(x) in it and simplifying. Option (C) is trickier so try it at the end.
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