well, we can take a peek at this from the standpoint of moving from the right towards 0, but never getting there.
[tex]e^{-\frac{5}{x}}\implies \cfrac{1}{e^{\frac{5}{x}}}\qquad \qquad \stackrel{x = 1}{\cfrac{1}{e^{\frac{5}{1}}}}\implies \cfrac{1}{e^5}\qquad \qquad \stackrel{x=0.000001}{\cfrac{1}{e^{\frac{5}{0.000001}}}}\implies \cfrac{1}{e^{500000}}[/tex]
as "x" is moving towards 0, the denominator is becoming larger and ever larger, whilst the numerator is remaining the same, thus the fraction is become ever smaller, going towards = 0.
