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Numerical expressions and expressions containing variable

Надя Данильченко
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Basic math course includes elementsalgebra. The study of elements of the algebra in primary school promotes synthesis of knowledge on the number of students, arithmetic and relationships. Students receive an introduction to the mathematical expression x, get acquainted with the letter symbols, solve problems , ychatsya solve simple equations and inequalities acquire the initial skills to solve problems in one step using the equations - it is the first.

Creation and development of ideas of students about numerical expression

The concept of the numerical expression in primary school children formed in close connection with the study of the arithmeticcal action. Reveal the essence of each of these steps:

  1. First stage - the study of addition and subtraction within 10. During this period, the signs "+" and "-" in the examples of the form 2 + 3; 5 - 1 acts only as shorthand for the word "add" and "subtract". It is reproduced in the process of reading: to number two plus three, will toeb. The work plan introduces the term "example". Such recording is 2 + 1 = 3; 3 + 2 = 5 is referred to as examples of the addition. During the teacher "discreetly" introduces the term "expression". For example, the proposed exercise: write and calculate expression : to add the number 4avit 5, 6 plus 3; 7 reduced to 6; 9 subtract the number 6; 10 minus 8. Any interpretation of the term "expression" is not supplied, the value is disclosed in the application in different situations, in different kinds of assignments. If students do not understand the problem, the teacher changes the wording complements it. The phrase "the word" on the lanetion phase is not used.
  2. In the second stage (with the introduction of brackets) reveals a different meaning signs of action - a sign of the action is given by: the 5 + 2 - is the sum of the numbers 5 and 2; 9 - 3 - a difference of numbers 9 and 3. The realization that expression appears as a separate component of action is achieved in the process of solving exercises beforeconstruing an expression read and write.
  3. The third stage falls on the beginning familiarize with activities of multiplication and division.
  4. The fourth step is considered a rule evaluating expressions containing action of different degrees (in any order), served the wording of the rules of order fulfillment operations. The EmblemGUSTs with this material perform direct message and reading of the rules by the book.

Students are taught how to read, write and calculate compiled expression < / span> ( expression in a few steps.) This sum, difference, product, and the proportions in which one or two components of the given expression. This is a complex for kids stuff. Therefore it is necessary to analyze the structure of -dvuh expressions. Here is a sample conversation that can take place in the process of analyzing expression : 40 - 20: 4.

So, it is clear that In order to explore the next stage, it is necessary to know well the previous.

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