Function is a mathematical relationship between two variables that can express as a mathematical equation. Let x is a function of y. The expression of this function mathematically is as,
y = f(x)
In each value change in x is effect on changing of the value of y.
Let,
y = x²+2x+3
If x is a function of y, then for the value of x 1, 2, 3 the value of y is changes.
If x = 1, then
y = 1+2+3 = 6
If x = 2, then
y = 4+4+3 = 11
For the changing of the value of x the value of y is changes, because y is a function of x.