# How do you simplify and find the excluded value of (x^2+x+1)/(1-x^2)?

Apr 26, 2017

see explanation.

#### Explanation:

Factorise the denominator using the $\textcolor{b l u e}{\text{difference of squares}}$

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

The denominator of the function cannot equal zero as this would make it $\textcolor{b l u e}{\text{undefined}} .$Equating the denominator to zero and solving gives the values that x cannot be.

$\text{solve } \left(1 - x\right) \left(1 + x\right) = 0$

$\Rightarrow x = 1 \text{ or " x=-1larrcolor(red)" excluded values}$