"The Value of Algebraic Expressions" PPT Courseware 3

Description

"The Value of Algebraic Expressions" PPT Courseware 3

1. Learning objectives:

1. Understand the meaning of the values ​​of algebraic expressions and be able to calculate the values ​​of algebraic expressions.

2. Be able to use algebraic expressions to solve simple practical problems.

2. Key points and difficulties in learning:

Key Points: Understand the meaning of the values ​​of algebraic expressions and be able to accurately calculate the values ​​of algebraic expressions.

Difficulty: Use algebraic expressions to solve practical problems.

Example 1: 50 students from Class 2 of Senior High School in a school participated in a tree-planting activity organized by the school. 2/5 of the students each planted a tree, and the rest each planted (a+1) trees.

(1) Can you use an algebraic expression to express the tree they planted together?

Solution: 50a+30

(2) When a=5, how many trees did the whole class plant?

Solution: When a=5, 50a+30

=50� 5+30

=280(tree)

step

1. Write the value of the letter, that is, "when...".

2. Write the algebraic expression of the required value.

3. Substitute the values ​​of the letters into the same letters in the algebraic formula, and obtain the calculation result according to the operation relationship.

Notice

1. You can also substitute first and then calculate. The substitution step is essential.

2. In the process of substituting numbers into letters, sometimes it is necessary to add operational symbols or brackets appropriately. For example, a multiplication sign is added to the multiplication relationship between numbers. When the base of a power is a fraction or a negative number, brackets must be added to the base.

Practice in class:

1. The mass of human blood accounts for about 6% to 7.5% of human body weight.

(1) If someone weighs a kilogram, what is the approximate range of his blood mass?

(2) Liangliang’s weight is 35 kilograms. What is the approximate range of his blood quality?

(3) Estimate the quality of your own blood.

Solution: (1) His blood mass is approximately between 6%a kg and 7.5%a kg.

(2) The mass of bright blood is approximately between 2.1kg and 2.625kg.

(3) The blood mass of a person weighing 50 kilograms is approximately between 3 kilograms and 3.5 kilograms.

Class summary:

1. Substituting specific numerical values ​​for letters in the algebraic formula for calculation must follow the order of operations specified in the algebraic formula.

2. Be clear about the operation symbols.

3. Pay attention to the writing format:

Solution: when...

Original formula =……

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For more information about the "Value of Algebraic Expressions" PPT courseware, please click on the "Value of Algebraic Expressions" ppt tag.

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"Value of Algebraic Expressions" PPT Courseware 6 Review: 1. What is a monomial? An algebraic expression that only contains the product of numbers and letters is called a monomial. 2. How to determine the coefficient and degree of a monomial? The sum of the exponents of all letters in a monomial is called the degree of the monomial. 3. What...

"Value of Algebraic Expressions" PPT courseware 5:

"Value of Algebraic Expression" PPT Courseware 5 Definition of the value of algebraic expression: According to the needs of the problem, use specific numerical values ​​to replace the letters in the algebraic expression, and calculate according to the operational relationships in the algebraic expression. The result obtained is called the value of the algebraic expression. Example 1 When a= When -2b=-3, find the algebraic expression 2..

"Value of Algebraic Expressions" PPT courseware 4:

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Update Time: 2024-07-01

This template belongs to Mathematics courseware Qingdao Edition Seventh Grade Mathematics Volume 1 industry PPT template

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