Toán Tiếng anh: Giá trị biểu thức đại số

Week 24 
Period 52 §2. THE VALUE OF AN ALGEBRAIC EXPRESSION 
I/ Objectives: 
- The knowledge: Students can apply the knowledge learned in solving problem on 
algebraic expression 
- The skills: Students have ability to calculate quickly, perform operation on algebraic 
expression exactly. Students have skills presenting Math solutions in English well 
- The attitude: Students have self-discipline in learning and group activities. There is a 
dynamic, creative life 
II/ Vocabulary: 
- Value: Giá trị 
III/ Teaching and students aids: Book, notebook, ruler, sheet 
IV/ Content: 
 1/ Class organization: 
- Greeting 
- Checking attendance: How many students absentees on today ? 
2/ Check up: 
a/ Rewrite formula the area of a rectangle whole length and breadth are x(cm) and y(cm) 
respectively 
b/ If x = 3(cm) and y = 5(cm). Find the area of a rectangle ? 
Give remark to student answer: - Is your solution right or wrong ? 
- What knowledge in the lesson have you used ? ( formula the 
area of a rectangle ) 
3/ New lesson: 
Teachers activities Students activities Content 
Introduce how we can find 
the value of an algebraic 
expression from two 
example 
Solve similar exercises 
If p =2 find the value of 
a/ 4p + 7 
b/ -3p
2
 + 4p – 6 
Ask two students to pre 
present write on the board. 
Who can ? 
Give remark to the students 
answers: Is your solution 
Look and write on the 
notebook 
Slove the following problem 
1/ The value of an 
algebraic expression: 
Example 1: The following 
an express: 2m + n. Putting 
the value of m = 9 and n = 
0,5 in 2m + n 
Solution: 
Putting the value of m = 9 
and n = 0,5 in 2m + n. We 
get: 2.9 + 0,5 = 18,5 
They said: 18,5 is value of 
expression 2m + n at m = 9, 
n = 0,5 
Example 2: Find the value of 
the following expression 3x
2
-5x + 1 at x = -1; x = ½ 
Solution: 
Substituting x = -1 in 3x
2
 -5x 
+ 1 we get 3.(-1) – 5(-1) + 1 
= 9 
Similar: x = ½ in 3x
2
 -5x + 1 
we get 3.(1/2) – 5(1/2) + 1 = 
-3/4 
right or wrong ? 
Ask a student to represent in 
front of class. Who can do it 
? 
Ask a student represent in 
front of class. Who can 
answer ? 
Repeat the statements above 
Slove the following problem 
A student represents on the 
board 
Slove the following problem 
Answer: 48 
Thus: There are s number of 
stuations in which we need 
to find the value of an 
expression 
2/ Applied: 
? 1 Find the value of the 
following expression 3x
2
 – 
9x at x =1 and x = 1/3 
Solution: 
Putting the value of x =1 in 
3x
2
 – 9x we get 3. 12 – 9.1 = 
- 6 
Substituting: x = 1/3 in 3x
2
 – 
9x we get 3.(1/3)
2
 – 9.1/3 = -
8/3 
? 2 Read the number , your 
choose is correct. The value 
of following expression x
2
y
2
at x = 4 and y = 3 
-48 144 – 24 48 
 4/ Consolidation: 
Exercise: Who can do it ? 
6/28: Puzzle: Divide into three group and complete the following exercise. Students do all within 5 
minutes. Give remark to student answers 
- 7 51 24 8,5 9 16 25 18 51 5 
L Ê V Ă N T H I Ê M 
7/29: Find the value of the following expressioon when m = -1 and n = 2 
a/ 3m – 2n 
b/ 3m + 2n – 6 
 5/ Homework: 
- Review all the lesson that we do today 
- Solve the following exercise below: When a = 0 and b = -1 find the value of the given 
expressions 
 a/ 2a + 2b 
 b/ a
2
 + 2ab + b
2
 c/ 2a
2
b + 2ab
2
 - ab