Using letters to represent numbers can express quantitative relationships concisely, and can also express the results of operations.

In expressions containing letters, the multiplication sign between numbers and letters, or between letters and letters, can be recorded as "•" or omitted. When the multiplication sign is omitted, the numbers should be written in front of the letters. For example, 6×a=6•a=6a.

When expressing a division equation using an expression containing letters, the calculation result should be written in the form of a fraction.

When 1 is multiplied by any letter, both the 1 and the multiplication sign can be omitted.

When two identical letters are multiplied, they can be written as the square of the letter; when several different letters are multiplied. The writing results are generally arranged in alphabetical order. a×b=a² (pronounced a squared), a×b×c=abc

express quantitative relationship

Express the laws of operations and properties of operations

Use letters to express calculation formulas

First write out what number the letters equal, then write out the original formula, and then substitute the numerical values ​​into the original formula to evaluate. (When substituting data into the equation to evaluate, the omitted multiplication sign in the original equation must be restored).

When the letters contained in the same formula take on different numerical values, the values ​​of the formula obtained are generally also different.

The meaning of the equation

The meaning of the equation

The relationship between equations and equations

Solution of the equation

Solving equations

The relationship between the various parts of the four arithmetic operations

Properties of equations

First write the word "Jie", then add a colon ":". In the process of solving equations, write one equation in each line, the unknowns are written on the left side of the equation, and the equal signs of the equations in each line should be aligned.

significance

step

Precautions