#### Note 8.2.1.

If we try to evaluate the fraction \(\dfrac{a^2+1}{a-2}\) for \(a=2\text{,}\) we get \(\dfrac{2^2+1}{2-2}\) or \(\dfrac{5}{0}\text{,}\) which is undefined. When working with fractions, we must exclude any values of the variable that make the denominators equal to zero.