First of all, as a function, you must ask for an x, which can only correspond to a y (take y=x as an example. But one y can correspond to multiple x)

The equation does not require this.

Equation (English: EQUATION) is an equation that represents the equality between two mathematical expressions (such as two numbers, functions, quantities and operations), and there is usually an equal sign "=" between them. Equations do not need reverse thinking, but can be listed directly, including unknowns. It has many forms, such as one-dimensional linear equation, two-dimensional linear equation and so on. , widely used in mathematics, physics and other scientific applications.

Generally speaking, there is not much difference between the two in solving problems, and the difference is mainly in the meaning, that is to say, the function is included in the equation (this is my personal understanding and I hope it will be helpful to LZ).

Typing is not easy. If you are satisfied, please adopt it.