The function is
.
Horizontal line test:
\A function
has an inverse
if and only if no horizontal line intersects its graph of the function in at most one point.
Graph :
\Graph the function
.
Draw the horizontal line
.

Observe the graph:
\ The horizontal line
touches the graph of the function more than once.
The function is not an one-to-one, because it does not satisfy the horizontal line test.
\Therefore the inverse of the function does not exist.
\The inverse of the function does not exist.