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The function f(x)=x−2x+1,x≠−1f(x) = \frac{x - 2}{x + 1}, x \neq -1 is increasing when (Where R\mathbb{R} is a set of real numbers)

Solution

✅ Correct Option: 2

A function is increasing when its derivative f′(x)>0f'(x) > 0.


Given f(x)=x−2x+1f(x) = \frac{x - 2}{x + 1}

Using the quotient rule with u=x−2u = x - 2 and v=x+1v = x + 1:

f′(x)=(x+1)(1)−(x−2)(1)(x+1)2f'(x) = \frac{(x+1)(1) - (x-2)(1)}{(x+1)^2}

f′(x)=x+1−x+2(x+1)2f'(x) = \frac{x + 1 - x + 2}{(x+1)^2}

f′(x)=3(x+1)2f'(x) = \frac{3}{(x+1)^2}


For f′(x)>0f'(x) > 0:

3(x+1)2>0\frac{3}{(x+1)^2} > 0

The numerator 33 is always positive.

The denominator (x+1)2(x+1)^2 is always positive for all x≠−1x \neq -1.

Therefore f′(x)>0f'(x) > 0 for all x≠−1x \neq -1.


The function is increasing for x∈R−{−1}x \in \mathbb{R} - \{-1\}.

This represents all real numbers except −1-1.

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