Question
Let $f=\left\{\left(x, \frac{x^2}{1+x^2}\right): x \in R\right\}$ be a function from R into R . Determine the range of f .

Answer

Here $f(x)=\frac{x^2}{1+x^2}$
Put $y=\frac{x^2}{1+x^2}$
$\Rightarrow y+y x^2=x^2$
$\Rightarrow x^2(1-y)=y$
$\Rightarrow x^2=\frac{y}{1-y}$
$\Rightarrow x= \pm \sqrt{\frac{y}{1-y}}$
$\frac{y}{1-y} \geq 0$
$\Rightarrow \frac{y}{y-1} \leq 0$
$\Rightarrow 0 \leq y<1$
$\Rightarrow y \in[0,1)$
$\therefore$ Range of $f(x)=[0,1)$

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