# How do you use the vertical line test to show #x^2-4y^2+4=0# is a function?

##### 1 Answer

Jun 15, 2015

It's self-explanatory; draw a vertical line and see if it intersects more than once with the curve. If so, it's not a single-valued function and therefore it's not a single function.

And evidently, this is not one function, but two. You have a