An equation is an equation that represents the equal relationship between two mathematical expressions (such as two numbers, functions, quantities and operations), and the value of the unknown quantity that makes the equation hold is called "solution" or "root". The process of finding the solution of the equation is called "solving the equation".

By solving the equation, we can avoid the difficulty of reverse thinking and directly list the equations with the quantity to be solved. There are many forms of equations, such as one-dimensional linear equation, two-dimensional linear equation, one-dimensional quadratic equation and so on. , can also be combined into equations to solve multiple unknowns.

An equation must be an equation, but an equation is not necessarily an equation.

Example: a+b= 13 conforms to the equation, and there are unknowns. This is an equation and an equation.

1+ 1=2 , 100× 100= 10000。 These two formulas are consistent with the equation, but there are no unknowns, so they are not equations.

In the definition, the equation must be an equation, but there can be other equations, such as 1+ 1 = 2,100×10000 =10000, all of which are equations. Obviously, the range of the equation is larger.