"Primary Function" PPT Courseware 3

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"Primary Function" PPT Courseware 3

1.What is a function?

In a certain change process, there are two variables x and y. If an x ​​value is given, a y value is determined accordingly, then we call y a function of x, where x is the independent variable and y is the dependent variable.

2.What are the expressions of functions?

Functions can be expressed in three ways: images, tables, and algebraic expressions.

Discuss

The above two functional relationship expressions: (1)y=3+0.5x

(2) y=100-0.18x, let’s discuss, is there any relationship between these two functional expressions? Please communicate among the groups.

Linear function: If the relationship between two variables x and y can be expressed in the form of y=kx+b (b is a constant, k is not equal to 0), then y is said to be a linear function of x. (x is the independent variable, y is the dependent variable.)

When b=0, y is said to be a proportional function of x.

The monthly telephone rental fee in a certain area is 25 yuan. On this basis, you can make 50 free local calls (3 minutes each time). After 50 times, the fee is 0.2 yuan each time.

(1) Write the functional relationship between the monthly telephone fee y (yuan) and the number of calls x (x>50);

(2) Find the phone bill for 150 calls per month;

(3) If the call fee in a certain month is 53.6 yuan, find the number of calls in that month.

practice

Among the following statements, the one with a proportional function relationship is ().

A. The area of ​​the rectangular flower bed remains unchanged, and the relationship between length y and width x;

B. The perimeter of the square remains unchanged, and the relationship between the side length x and the area S;

C. One side of the triangle remains unchanged, and the relationship between the height h on this side and S;

D. The area of ​​the circle is S, the radius is r, and the relationship between S and r.

my country's current personal wage and salary income tax collection methods stipulate that no tax is levied on the portion of the monthly income below 1,600 yuan; 5% income tax is levied on the portion of the monthly income exceeding 1,600 yuan but less than 2,100 yuan... For example, a person's monthly income is 1,960 yuan, The personal wage and salary income tax he should pay is (1960-1600) × 5% = 18 (yuan).

(1) When the monthly income is greater than 1,600 yuan but less than 2,100 yuan, write down the relationship between the income tax payable y (yuan) and the monthly income x (yuan).

Solution: When the monthly income is greater than 1,600 yuan but less than 2,100, y=0.05×(x-1600).

(2) A person's monthly income is 1,760 yuan. How much income tax should he pay?

Solution: When x=1760, y=0.05×(1760-1600)=8 (yuan).

(3) If a person pays income tax of 19.2 yuan this month, how much is his wages and salary this month?

Solution: Suppose this person’s salary and wages this month are x yuan, then 19.2=0.05×(x-1600),

x=1984.

That is, this month’s wages and salaries are 1,984 yuan.

Keywords: One-time function courseware, Beijing Normal University edition eighth-grade mathematics volume PPT courseware, eighth-grade mathematics slide courseware download, one-time function PPT courseware download, .ppt format

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Update Time: 2024-06-20

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