The coordinate plane is also called a Cartesian Plane. Function. A function is a relationship where there is only one output for every input. In other words, for every value of x, there is only one value for y.
It does not pass the vertical line test. A vertical line can touch the graph in more than one point.
To be a function, every x can have only one y value. On this graph almost every single x has two y's. For example when x is -6, the y is 2 and also 8. Not a function.
