1. Arrange rational numbers in the order of addition and subtraction.

2. For the addition of numbers with the same sign, add their absolute values, and then keep the original sign.

3. For the addition of numbers with different symbols, subtract their absolute values, and then add symbols to the numbers with larger absolute values.

4. If there are brackets, first calculate the addition and subtraction operations in brackets.

5. Calculate step by step according to the above steps until the final result is obtained.

For example:

Hypothetical calculation: 5+(-3)-2+ 1/2.

Calculate according to the steps:

1. Arrange rational numbers in order of addition and subtraction: 5+(-3)-2+ 1/2.

2. For the addition of numbers with the same sign: 5+(-3) = 2, and keep the negative sign.

3. Addition of different numbers: 2-2 = 0.

4. Finally add the score: 0+ 1/2 = 1/2.

So the result of 5+(-3)-2+ 1/2 is 1/2.

When performing rational number addition and subtraction mixed operation, you should pay attention to:

1, pay attention to the use of symbols: the "+"sign can be omitted before the positive number; Negative numbers are indicated by "-"; Correct use of signs in operation.

2. Calculate according to the operation order: do the operation in brackets first, then multiply and divide, and finally add and subtract.

3. Pay attention to the simplification of fractions: in the process of operation, if a fraction appears, it should be simplified to the simplest form as needed.

The function of rational number addition and subtraction mixed operation is

1. Simplified calculation: rational number addition and subtraction mixed operation can transform complex numerical calculation problems into simple addition and subtraction operation, simplify calculation process and improve calculation efficiency.

2. Establish a mathematical model: the mixed operation of rational number addition and subtraction is the basis of establishing a mathematical model. By abstracting practical problems into the form of rational number operation, a mathematical model can be established for further analysis, optimization and prediction, so as to draw more accurate conclusions and decisions.

3. Cultivate logical thinking: the mixed operation of rational number addition and subtraction needs symbolic operation and logical reasoning, which can cultivate learners' logical thinking and mathematical thinking ability and improve their ability to solve and analyze problems.