Question

find the domain of the following rational expression: 1/(x^2-4)

Answer 1

Whenever the denominator=0 the function is undefined so
x^2-4=0
x={-2,+2} is undefined, therefor
The Domain is all x not equal to plus or minus 2

Answer 2

x such that x is not equal to 2 or -2, that is, all real x except 2 and -2