For what value of c is the relation a function?

Answer: [tex]c\ \epsilon\ \mathbb{R}\text{ where }c\neq 2,12,-1,0[/tex]
Step-by-step explanation:
We know that a function is a special kind of relation between two variables say x and y such that each input corresponds to exactly one output.
In the given relation , we need only one output corresponds to each input.
Then to fulfill the condition to become a function, we can take any value for c belongs to the set of real numbers other than the values which the relation already has taken as input .
Then [tex]c\ \epsilon\ \mathbb{R}\text{ where }c\neq 2,12,-1,0[/tex]