What makes a rational expression undefined?

a rational express ion undefined when the denominator is 0 because we cannot dvide by 0. For example, 9/x is undefine when x is 0 because we would be dividing by 0. Similarly 2/(7-x) is undefined for x=7 because we once again have a zero in the denominator.

To find where a rational expression is undefined, set the denominator equal to 0

so if we have p/q where q is any number or expression, set and solve q=0

From, Doctor Huge Dick