if the equation is x/(x^2-4) then I will solve it here
it's rational
therefor we can't have any impossibles like dividing by zero and square root of -1 an d stuff
f(x)=x/(x^2-4)
we know that the denomenator cannot be equal to zero so the numbers you cannot user are the numbers that will make the bottom number zero
so x^2-4=0
x^2=4
x=-2 or 2
so x cannot be -2 or 2, but it can be all other numbers so
domain=all numbers except -2 and 2