Question

Consider a function f(x) such that f(5x) =x-5/5x-1. Find f(x) and hence write down the domain of f(x).
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Answer 1

Answer:

$f(x) = \frac{x - 25}{5x - 5}$

Domain: $x \ne 1$

Step-by-step explanation:

Given

$f(5x) = \frac{x - 5}{5x - 1}$

Required

Determine f(x) and its domain

To determine f(x), we replace 5x with x in f(5x)

So, we have:

$f(5x) = \frac{\frac{5x}{5} - 5}{5x - 1}$

$f(x) = \frac{\frac{x}{5} - 5}{x - 1}$

Take LCM

$f(x) = \frac{\frac{x - 25}{5}}{x - 1}$

$f(x) = \frac{x - 25}{5} * \frac{1}{x-1}$

$f(x) = \frac{x - 25}{5x - 5}$

To get the domain, we set the denominator as

$5x - 5 \ne 0$

$5x \ne 5$

$x \ne 1$