Equation is a mathematical concept, which expresses an equality relationship, that is, in a mathematical expression, there is an equal relationship between the mathematical quantities on both sides of the equal sign.

Specifically, the equation can be defined as follows.

Equations with unknowns: Equations usually consist of an equal sign and two expressions, and at least one expression on both sides of the equal sign is unknown. Unknown numbers can be letters, symbols or numbers, but they represent unknown quantities or values.

Represents an equation: an equation represents an equation, that is, the mathematical quantities on both sides of the equal sign are equal. This equation is the core of the equation, which provides us with clues or clues to solve the problem.

Solving the unknown: the biggest purpose of the equation is to solve the unknown. By operating and transforming the unknowns in the equation, we can find one or more solutions that satisfy the equation, and these solutions are the values of the unknowns we need.

The equation is applied as follows:

1. Solving the quadratic equation of one variable: The quadratic equation of one variable is one of the most common quadratic equations, which can be used to solve some practical problems, such as calculating area, volume, average value, etc. By solving the equation, we can get the value of the unknown quantity that satisfies the equation.

2. Modeling: Equations can be used to establish various mathematical models, such as linear regression model and quadratic curve fitting model. These models can be used to describe and predict various phenomena and laws in the real world, such as problems in economics, biology, physics and other fields.

3. Calculating physical quantities: In physics, equations can be used to calculate various physical quantities, such as mass, speed, acceleration and force. By solving the equation, the value of the physical quantity satisfying the equation can be obtained.

4. Optimization problem: Equation can be used to solve some optimization problems, such as the shortest path problem and the minimum cost problem. By solving the equation, the optimal solution satisfying the equation can be obtained.

5. Signal processing: In the field of signal processing, equations can be used to describe the characteristics of signals, such as frequency, amplitude and phase. By solving and analyzing the equation, the characteristics of signal spectrum and filtering effect can be obtained.