To find the point for removable discontinuity, h(x)=x^2-4x-12/, we have to find the roots of the numerator so that when we find one of those roots, plugging the root into the equation gets a denominator of zero. So we have to find those roots with the following rules:
h(x)=x^2-4x-12
h(x)=(x-6)(x+2)
So we can place either (x-6) or (x+2) at the denominator, and find that either 6 or -2 creates the point of removable discontinuity.
