Chuong II 2 Ham so bac nhat

Activity 2: Increasing/ Decreasing Linear Functions 15 mins Task 2: Evaluate the values of y then fill in the following table: a.. T: Depend on your tables, which is the increasing funct[r]

SCHOOL: AN LAC MIDDLE SCHOOL

MEMBERS:

1 NGUYỄN THỊ DIỄM THÚY

2 LÊ HOÀNG UYÊN

3 PHAN TUYẾT MAI

LESSON PLAN OF GRADE 9

CHAPTER II LINEAR FUNCTIONS LESSON 2 LINEAR FUNCTIONS

I GOALS

- To understand the concept of linear functions

- Determine if a linear function is increasing or decreasing

- Interpret linear function models

II PRIOR KNOWLEDGE

Students have to had prior knowledge of:

- The concept of functions

- The graphs of functions

- Increasing functions and decreasing functions

III LEARNING OUTCOMES

At the end of this lesson, students will be able to:

- Recognise the formula of linear functions in a variety of contexts

- Identify the increasing linear functions and decreasing linear functions

- Apply the knowledge of linear functions to solve problems in both theoretical and practical contexts

IV PROCEDURE

Notes:

T := Teacher’s activity.

S := Students’ activity.

Activity 1: Opening problem (15 mins)

A bus from the Can Tho Bus Station to Ho Chi Minh City with the average speed is 42km per hour Given that the Can Tho Bus Station is located 5 km far from the Center

of Can Tho City

a After departed an hour, how many kilometers did the bus travel?

b After departed an hour, how far (in km) is the bus from the center of Can Tho city?

c Calculate the distance from the center of Can Tho city to the bus after the following period time given then complete the following table:

Distance(km

S: Work in pairs

a 42km

b 47km

c

Time(h) 1 2 3 t Distance(km

42t  5

T: After t hours, the distance from the center of Can Tho city to the bus can solve by this

equation:

42 8

s t

Or we can rewrite: y42x8

The function above is called a linear function.

Definition:

Linear functions are functions that fit the form:

yf x  x with a, b are real numbers and a  0.

Task 1: Work in groups to finish the task in 3 mins.

Which one of the following functions are linear functions?

Find their coefficients a, b of those linear functions?

i y 1 5 x ii y2 x iii x y  2. iv y 3.

x

y  

S:

i Linear function a5;b 1.

ii Linear function a2;b0.

iii Linear function a1;b2.

iv Not a linear function a  ( Note: It can be called a nonlinear function).0.

v Not a linear function (The power of x is 2).

vi Linear function

1

; 1

2

a b

Activity 2: Increasing/ Decreasing Linear Functions (15 mins)

Task 2: Evaluate the values of y then fill in the following table:

a

2 1

b

2 1

S: Answer

a

2 1

b

2 1

T: Depend on your tables, which is the increasing function? and which is the decreasing

function?

S:

* y2x  is the increasing function.1

* y2x  is the decreasing function.1

Properties:

The linear function yaxbincreasing in ℝ if a 0.

The linear function yaxbdecreasing in ℝ if a 0.

Task 3: Determine which linear functions in task 2 are increasing linear function and

which one is decreasing

S: Answer

Increasing linear functions :

2 ;

y x x y 2; 1

2

x

y  

Decreasing linear functions : y 1 5 x

Activity 3: Language Focus and Practice (13 mins)

Task 4: Fill in the blank (…) with the correct words, formulae or numbers:

A …….………… has the following form

y x with a, b ……… and ………

The independent variable in above function is … and the dependent variable is …

y x is ………if a 0.

y x is decreasing if …….

Task 5: Return to the Opening problem.

Given the distance from center of Can Tho city to Ho Chi Minh city is about 176km How long does it take the bus to travel from Can Tho Bus Station to Ho Chi Minh city?

Answer: 4 hours.

Homework: (2 mins)

You are working at a car dealer that pays you a monthly salary of 3.500.000 VND

The dealer will also pay you 500.000 VND in commission for every car you sell

a What is the independent and dependent variable and why ?

b What are the units of measure?

c Write out the calculation reguired to compute your pay if you sell 0 cars, 1 cars, 2 cars and 3 cars