Answer :

Let's simplify the given fraction step by step:

The expression we need to simplify is:
[tex]\[ \frac{x-1}{1-x} \][/tex]

First, observe the relationship between the numerator and the denominator. Notice that the numerator, \(x-1\), and the denominator, \(1-x\), are closely related. Specifically:
[tex]\[ 1 - x \text{ is actually } -(x - 1) \][/tex]

This means:
[tex]\[ 1 - x = - (x - 1) \][/tex]

So, the given fraction can be rewritten as:
[tex]\[ \frac{x-1}{1-x} = \frac{x-1}{-(x-1)} \][/tex]

Now, we can simplify this by factoring out the negative sign in the denominator:
[tex]\[ \frac{x-1}{-(x-1)} = -1 \][/tex]

Therefore, the simplified form of the given expression \(\frac{x-1}{1-x}\) is:
[tex]\[ -1 \][/tex]

The correct answer is A. [tex]\(-1\)[/tex].