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 atmost once.

The function is an one-to-one, because it satisfy the horizontal line test.

Therefore the inverse of the function is exist.

The inverse of the function is exist.