determine the values for which the rational expression is undefined.Z = __,__

Fort the function:
[tex]\frac{x-1}{x^2-2x-8}[/tex]The expression is undefined when the denominator is 0, then:
[tex]x^2-2x-8=(x+2)(x-4)[/tex]This expression is equal to 0 when x= -2 or 4.
The expression:
[tex]\frac{x-1}{x^2-2x-8}[/tex]Is undefined for x= -2 or x=4