2. The difference between (2x-3y) and (X-Y) is twice ().

2. The width of the rectangle is a, and the aspect ratio is 1, so the perimeter of this rectangular line is ().

3. Simplify first and find (2) 5 (the square of 3a-the square of ab)-(the square of ab+the square of 3a-b), where A = 1/2 and B=- 1.

4. It is known that the perimeter of a triangle is 3A+2B, in which the length of the first side is A+B, and the length of the second side is smaller than that of the first side 1. Find the length of the third side.

Comprehensive application

5. Formulate a number that is five times larger than half of Y and six times smaller than Y, and calculate the sum of these two numbers.

6. Given A=X3 cube +3Y cube -XY square, B=-Y cube +X cube +2XY square, where x = 1/3 and Y=2, find the value of a-b.

7. It is known that the quadratic power b|m+ 1| of (m-2)a is the quadratic power of 1m-2m+65438+ by finding the values of the following algebraic expressions and comparing the results of (1)(2).

What does the letter 1. mean?

Selected Mathematics Exercises of Grade One in Junior High School

Fill in the blanks

1. A dozen pencils, 12, and _ _ _ _ _ _ _;

2. The distance from Xiao Ming to school is, and the time it takes is, so the walking speed of Xiao Ming to school is _ _ _ _ _ _;

3. The unit price of a cost is yuan, so it needs _ _ _ _ _ yuan.

Second, answer the question.

1. As shown in the figure, dig a square from the circle and use r to represent the shadow area.

2. As shown in the figure, a square with a side length of 1 is divided into n times. What is the area of the smallest quadrilateral?

Reference answer:

I. 1.2.3.

2. 1. (hint: if you answer the picture, divide the square into two triangles, where the area of the triangle is.

2. (Hint: The area of the smallest quadrilateral is divided by one, two, three … times, followed by minutes.

2. Algebraic expressions

Selected exercises

First, multiple choice questions

1. Among the following options, the one that meets the requirements of algebraic writing is ().

A B C D

2. If the train speed is km/h, it can run in a few minutes ()

One kilometer, b kilometers, c kilometers and d kilometers.

3. The algebraic expression "twice the difference of sum" is correct ()

A, B, C and D.

4. After the price of a certain brand of color TV is reduced by 30%, the price of each set is RMB, so the original price of each set of color TV of this brand should be ()

A yuan b yuan c yuan d yuan

Second, fill in the blanks

1. If the radius of the cone bottom is and the height is, the volume of the cone is _ _ _ _ _ _ _ _;

2. If the length, width and height of a cuboid are respectively, the surface area of this cuboid is _ _ _ _ _ _ _ _;

In a primary school, the number of female teachers accounts for 90% of the total number of teachers, and the number of male teachers is. The total number of teachers in this school is.

_______;

4. The terms of this algebraic expression are _ _ _ _ _ and _ _ _ _ _ _, and their coefficients are _ _ _ _ _ _ and _ _ _ _ _ respectively.

5. In the following calendar, circle any three adjacent numbers in a vertical column, and let the middle number be a, then the sum of these three numbers is _ _ _ _ _ _. (represented by an algebraic expression with a).

6. Please note the following points:

Please use natural numbers to represent the law you have guessed _ _ _ _.

With the rapid development of computer technology, the price of computers is falling. After a certain brand computer is reduced by M yuan, it will be reduced by 20%. Now the price is N yuan, so the original price of the computer is _ _ _ _ _ _ _.

8. As shown in the figure, observe the following square patterns, each side has a dot, and the total number of dots in each pattern is S. According to this law, it is inferred that the relationship between S and N is _ _ _ _ _ _.

Third, answer questions.

1. An X kg vegetable can be sold directly at Y yuan per kg without processing. If the weight is reduced by 20% and the price is increased by 40% after processing, how much can this vegetable sell for x kilograms after processing? If this vegetable is 1000 kg, it can be sold directly without processing, and it is 1.50 yuan per kg. How much can it be sold after processing? How much more than before processing?

2. Name three practical problems, in which the quantitative relationship can be represented by A and B. ..

3. As shown in the figure, a represents the area of the shaded part.

4.2. Write an algebraic expression containing only the letter X..

Requirements: (1) make this algebraic expression meaningful; (2) The range of the letter X is all real numbers; (3) The value of this algebraic expression is always positive.

Reference answer:

1. 1.c Tip: Look at the "Attention" on page 92 of the textbook.

2.d Tip: Minutes are hours, time speed = distance, that is.

3.c Tip: Pay attention to the operation sequence.

4.d tip: the original price is the current price.

2. 1.2.3. (hint: female teachers account for 90% of the total number of teachers, so male teachers should account for 10% of the total number of teachers).

4.。

5. Tip: You can get the answer by doing more experiments.

6. Tip: Observe the characteristics of each column of numbers vertically.

7. Tip: First, reduce the price first.

8. Have different ideas. For example, the points that make up a square can be regarded as the four parts shown on the answer sheet, and the answer is or.

Iii. 1. 1. 12xy yuan, 1680 yuan, 180 yuan.

(1) A and B represent the length and width of the rectangle respectively, so the area of the rectangle is (2) If A represents the unit price of an item and B represents the quantity of an item, then the total price of this item can be expressed as (3)a represents the speed of the car, and B represents the time of the car, which can represent the distance traveled by the car.

3. (Hint: As shown in the answer sheet, half of the shadow area is equal to the area of a quarter circle with radius A minus the area of two right triangles with right sides A)

4. The answer is uncertain, such as

3. Algebraic evaluation

Selected exercises

First, multiple choice questions

1. The following algebraic expression: the value of must be positive, with ().

A.1b.2c.3d. None of the above answers are correct.

2. The following table shows the corresponding value of the algebraic expression of each given value of X ... The algebraic expression that satisfies all the conditions in the table is ().

0 1 2 3

The algebraic value is 2- 1-4-7.

A.B. C. D。

3. When the value of algebraic expression is ()

13 BC

4. Calculate the algebraic value according to the calculation program as shown in the figure.

If the input value of x is, the output result is ()

A.B. C. D。

Second, fill in the blanks

1. As shown, fill in the form:

2. As shown in the figure, fill in the number:

1. Answer the form below.

Step 2 answer as shown in the picture

Reference answer:

1. 1. Tip: Only algebraic values are realized as positive numbers.

2.D

3.b Tip: The value that is easy to determine is an integer, so the algebraic value is fractional, and the fractional part is that you can get the result without writing.

4.c tip: therefore, the value of algebraic expression is to be calculated.

2. 1. Answer the form below.

Step 2 answer as shown in the picture

Three. 1.(1) (2)177 yuan

2.( 1) ,(2)40

3.( 1) square centimeter

(2) When

Original square centimeter