What is a counterexample to 'all linear equations are functions'?

Question

jhonyy9 · Answer

what mean ,,a linear equation" and when is an equation function ? 
do you can answering these questions please ? so will get the right answer sure

atsie · Answer

I'm sorry, but I kinda don't understand the questions your trying to ask.
What mean a linear equation?
When is an equation function?

bobo-i-bo · Answer

@Atsie Your terminology is very loose. Firstly I assume that by "linear equation" you mean an equation of the form y=mx+c. Being pedantic, technically a linear equation is not a function at all... it is an equation. Implicitly though, if you take y=f(x), then the linear equation would be function in terms of x. If you take x=f(y), then the equation would be a function in terms of y etc.
TL;DR Your question is not worded well. Do you know what a linear equation is?

sparrow2 · Answer

linear equations can be writesn as ax+by=c, if y=0 and a=1 then you get x=c which is not a function

queenie · Answer

https://answers.yahoo.com/question/index?qid=20100727194402AAHgxKk