find the range of 1/1-x2

We have, f (x) = \frac{1}{1 - x^{2}} \Rightarrow y = \frac{1}{1 - x^{2}} \Rightarrow y - x^{2} y = 1 \Rightarrow x^{2} y = y - 1 \Rightarrow x^{2} = \frac{y - 1}{y} \Rightarrow x = \sqrt{1 - \frac{1}{y}} Clearly x is not defined, when 1 - \frac{1}{y} < 0 o r 1 < \frac{1}{y} o r y < 1 . range (f) = \{y \in R : y ⩾ 1\}