The function f(x)=5^xf(x)=5x has horizontal asymptote y=0y=0 because as x to -oox→−∞, f(x) to 0f(x)→0 and no other asymptotes.
h(x)=5^x-2h(x)=5x−2 is a horizontal shift of f(x)f(x) by 2 units to the right, so the range is not impacted. That means the horizontal asymptote is still y=0y=0. The function has no other asymptotes.