Draw the graph of the function:
What is the formula of the asymptote?
Here the base is less than and therefore the graph is the mirror of the graph of the function:
We can show this quite easily. We write:
This means that the graph is the mirror in the -axis of the graph of:
The asymptote is the -axis, i.e. , because the larger the value of the more the graph approaches the -axis. We can verify this in the figure.