Should I tell what the function is or not?

1. How can you tell with what is a function and not?
2. How do you identify if the equation is function or not?

How can you tell with what is a function and not?

Use the vertical line test to determine whether or not a graph represents a function. If a vertical line is moved across the graph and, at any time, touches the graph at only one point, then the graph is a function. If the vertical line touches the graph at more than one point, then the graph is not a function.

How do you identify if the equation is function or not?

A function will only have one or zero outputs for any input. If there is more than one output for a particular input, the equation does not define a function. In order to be a function, each value of x should have, at most, one output value of y .