In functions, independent variables and dependent variables are relative, not absolute; Independent and dependent variables are not necessarily reversible.

For the function x=y+ 1, if the independent variable of this function is x, then the corresponding y is the dependent variable, which can be written as y=x- 1. In different examples, the independent variables are completely different, but the functions corresponding to the examples may be the same.

Whether the independent and dependent variables of a function are reversible depends on whether there is an inverse function in this function, and if there is, the independent and dependent variables are reversible; On the contrary, it is irreversible.

Give an irreversible example: y=x? When x can get all real numbers, this function has no inverse function, so the independent variable and the dependent variable are irreversible.