Question

Is y=-x+4 a function?

Answer 1

No

Explanation:

Its not a function because there wouldn't be a reasonable answer if you try solving the equation.

Answer 2

yes, it is a function

Explanation:

y = -x + 4 is a line. In order to be a function every input can have only one output. Any x you put into that equation will spit out only one y. It passes the vertical line test (ALL lines except a vertical line pass the vertical line test.) So it is a function.