Answer:
x = 2 and x = +2
Explanation:
It's essential that you use parentheses to clarify what's happening here:
h(x)=x-4/x^2-4 => h(x)=(x-4) / (x^2-4)
We have vertical asymptotes at x values at which the denominator (x^2 - 4) is zero. That would be x = 2 and x = +2.