Horizontal Line Test - Valid Reason? (1 Viewer)

[B35tY]

I was doing a prac paper and the question came up..

Why does this function have an inverse?

Can i just say:

"Because it passes the horizontal line test", or must i write out that for each y value the original function has one and only one x-value etc etc.

For the purposes of saving me a few seconds tomorrow in the trial, is it ok?

 

[pLuvia]

Or you can say it is a one-one function which is the same as the horizontal line test

 

[B35tY]

Cheers.