(1) rational number addition rule

1. Add two numbers with the same sign, take the same sign, and then add the absolute values.

That is to say, if a>0 and b>0, then A+B = a+b =+(| a |+| b |)；);

If a<0, b<0, then a+b=-(|a|+|b|).

2. Add two different symbols with different absolute values, take the symbol of the addend with larger absolute value, and subtract the one with smaller absolute value from the one with larger absolute value.

Two opposite numbers add up to 0.

That is, if a>0, b<0, and |a| >|b|, then a+b = a+b =+(| a |-| b |)；);

If a>0, b<0 and | a | < |b|, then a+b=-(|b|-|a|).

When a number is added to 0, it still gets this number.

(2) Arithmetic of rational number addition

Additive commutative law: When two numbers are added, the position of the addend is exchanged, and the sum is unchanged, that is, A+B = B+A..

Law of addition and association: When three numbers are added, the first two numbers are added or the last two numbers are added, and the sum is unchanged, that is, (a+b)+c=a+(b+c).

2 rational number subtraction rule

Subtracting a number is equal to adding the inverse of this number. The rational number subtraction rule can also be expressed as a-b=a+(-b). For example, (-3)-(-2)=(-3)+(+2)=- 1.

For the subtraction of rational numbers, it should be converted into addition first, and then calculated according to the addition rule of rational numbers.

3 addition and subtraction mixed operation of rational numbers Because subtraction can be converted into addition operation, the addition and subtraction mixed operation can be unified into addition operation, which is expressed as: a+b-c=a+b+(-c).

Use mind map: (It is recommended to save the printed mind map)

Knowledge inventory: through the head-tail effect of the brain, repeat the knowledge points learned every night and the next morning, and keep the memory peak continuously. Mind mapping is more interesting and faster than turning pages.

Check and fill in the gaps: when reviewing knowledge points, when you encounter unfamiliar knowledge points that you can't understand, mark symbols in the mind map, ask the teacher to solve the knowledge points and focus on the review.

Treatment of wrong questions: when encountering wrong questions, analyze the wrong questions, analyze the root of your own mistakes, find out the wrong knowledge points and mark them in the mind map. Every time you make a mistake, you may mark the same knowledge point many times. When reviewing again, you should know where your blind spots are and where your points are lost. When it is solved, the score will come up.

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