# How do you find the domain of (x+1)/(x^2 - 1)?

Apr 29, 2017

The domain of $\mathbb{R} - \left\{- 1 , 1\right\}$

#### Explanation:

We need

${a}^{2} - {b}^{2} = \left(a + b\right) \left(a - b\right)$

Let rewrite the function by factorising

$\frac{x + 2}{{x}^{2} - 1} = \frac{x + 2}{\left(x + 1\right) \left(x - 1\right)}$

Let $f \left(x\right) = \frac{x + 2}{\left(x + 1\right) \left(x - 1\right)}$

As we cannot divide by $0$, $x \ne 1$ and $x \ne - 1$

Therefore,

the domain of $f \left(x\right)$ is ${D}_{f} \left(x\right) = \mathbb{R} - \left\{- 1 , 1\right\}$