1. Operation sequence: in the absence of parentheses, the operation before parentheses is calculated first, and then the operation after parentheses is calculated. If there are both addition and subtraction, first calculate the previous addition and subtraction, and then calculate the latter addition and subtraction. For example, 4+5-3 should be understood as calculating 4+5=9 first, and then subtracting 3 from 9, that is, 9-3=6.
2. Associative law and commutative law: Addition and subtraction can be combined, that is, we can regard addition and subtraction as a whole. For example, 4+5-3 can be understood as calculating 4+5=9, and then subtracting 3 from 9, that is, 9-3=6. Addition and subtraction also follow the exchange law, that is, there is no order. For example, the results of 4+5-3 and 5+4-3 are all 6.
3. Simplify calculation: For mixed addition and subtraction operations, the calculation should be simplified as much as possible to reduce errors and improve the operation speed. Simplified calculation mainly includes eliminating brackets, merging similar terms, using associative law and commutative law. For example, 4+(5-3) can remove the brackets and directly calculate the result of 4+2=6.
The application scene of addition and subtraction mixed operation in mathematics;
1, solving practical problems: addition and subtraction mixed operations can be used to solve various practical problems, such as calculating the weight change of objects and calculating the sum and difference of a group of data. For example, if there are 10 apples in a box, then add 5 apples and take out 3 apples from the box, then you can calculate how many apples appear in the box by adding and subtracting.
2. Dealing with the probability problem: In the probability calculation, the mixed operation of addition and subtraction can be used to calculate the probability of occurrence and non-occurrence, as well as the probability of mutual cancellation. For example, if there are two events A and B, then you can use the mixed operation of addition and subtraction to calculate the probability that events A and B occur at the same time and the probability that events A or B occur alone.
3. Solving equations and algebraic expressions: addition and subtraction mixed operations can be used to solve unknowns in equations, such as solving linear equations with one variable. For example, if there is a one-dimensional linear equation, the formula is 3x+2= 10, then the unknown value of x can be solved by adding and subtracting mixed operations.