Firstly, the classification standard is determined, and the so-called equation refers to the equation with unknown numbers. If you look at the functional relationship, according to the number of unknowns, it is as follows:

Unary equation: y = f (x1);

Binary equation: Y=F(X 1, x2);

Three-variable equation: Y=F(X 1, X2, x3);

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N-variable equation: Y=F(X 1, X2, x3-xn);

Then, give examples respectively.

Three-variable equation: Y=F(X 1, X2, x3); For example:

There are 300 horses and 300 tiles. Three big horses, two ponies, two ponies, 1, and it's over at once.

Excuse me: Malaysia, pony, pony geometry?

Unary equation: y = f (x1); For example:

It's noon 12, and the hour hand and the minute hand coincide. How long will it take at least for the two hands to overlap again?

Binary equation: Y=F(X 1, x2); For example:

Without any auxiliary line, try to prove the "butterfly theorem" by equation.

N-variable equation: Y=F(X 1, X2, x3-xn);

Let y represent human life span, and there are n variables that affect human life span, such as heredity, temperature, humidity, drinking water, food, disease, personality, blood type, height, weight, mood and so on.