Vertical line test
The lines which is drawn parallel to y axis, or it can be y axis also , if cuts the graph of curve, at more than one point, then the curve drawn is not a function.
It is given that,the graph of a curve passes the vertical line test
The function can be linear, Quadratic,Cubic, that is it is a Many one function , that is for more than one value of x, it has a unique y.
vertical line you drew intersects the graph more than once for any value of x then the graph is not the graph of a function.
.there can be infinite values of m and n that can satisfy the above equation. for each value of m of m or n. there maybe infinite sets of solution for the above