# How do you decide whether the relation #x + y = 25# defines a function?

##### 1 Answer

For the relation

#### Explanation:

If we use the vertical line and there is only one unique point intersection with the graph of the given relation then it is a FUNCTION. Otherwise, it is not.

Kindly see the graph of

graph{(x+y-25)(y+10000x-15*10000)=0[-50,50,-25,25]}

How to test using the vertical line test

Example: the graph of

graph{(y^2-4y-2x)(y+10000x-15*10000)=0[-20,20,-10,10]}

Example: the graph of

graph{(2x^2-5x-3y)(y+10000x-2*10000)=0[-20,20,-10,10]}

God bless....I hope the explanation is useful.