Hebei education edition seventh grade mathematics first volume teaching plan 1
Cooperative exploration, exhibition and exchange
1. Question 1: A snail lives in the forest. Every day, he has to leave home to look for food. If the snail climbs to the right at a speed of 2 cm per minute, where is the snail after 3 minutes?
Rule: Right is positive, and now it is positive.
After 3 minutes, the snail should be at the () side () cm of the O point.
Can be expressed as: (+2)? (+3)
Question 2: If the snail keeps crawling to the left at a speed of 2 cm per minute, where is the snail after 3 minutes?
Rule: Right is positive, and now it is positive.
After 3 minutes, the snail should be at the () side () cm of the O point.
Can be listed as:
Question 3: If the snail has been crawling to the right at a speed of 2 cm per minute, where was the snail three minutes ago? Rule: Right is positive, and now it is positive.
Three minutes ago, the snail should be at the () side () centimeter of the O point.
Can be expressed as:
Question 4: If the snail has been crawling to the left at a speed of 2 cm per minute, where was the snail three minutes ago?
Rule: Right is positive, and now it is positive.
Three minutes ago, the snail should be at the () side () centimeter of the O point.
Can be expressed as:
2. Observe these four formulas:
(+2)? (+3)=+6 (-2)? (-3)=+6
(-2)? (+3)=-6 (+2)? (-3)=-6
According to your thinking about rational number multiplication, summarize and fill in the blanks:
Positive number multiplied by positive number is _ _ number: negative number multiplied by negative number is _ _ number:
The product of negative number multiplied by positive number is _ _ number: the product of positive number multiplied by negative number is _ _ number;
The absolute value of the product is equal to _ _ _ of the absolute value of each multiplier.
? Thinking: When a factor is 0, what is the product?
3. Try to summarize the rational number multiplication rule:
Multiply two numbers to get the same symbol, get different symbols, and then enter the absolute value.
Multiply any number by 0 and you will get it.
Third, try a knife.
1. Can you confirm the logo of the following products?
3 ? 7 product logo is; (-3)? 7 product logo is; 3? The sign of (-7) product is; (-3)? The sign of the product of (-7) is .2. Read first, then fill in the blanks:
(-5)x(-3)。 Multiply two numbers with the same sign.
(-5)x(-3)=+ () is positive.
5 x 3= 15 times the absolute value.
So (-5) x (-3)= 15.
Fill in the blanks: (-7) x 4 _ _ _ _ _ _ _ _ _ _ _ _ _ _
(-7)x 4 = -()？ ___________
7x 4 = 28？ _____________
So (-7)
x 4 = _ _ _ _ _ _ _ _ _ _ _ _
[Example 1] Calculation:
( 1)(-5)? (-6); (2)(-5)? 6;
(3)(-6)? (-0.45) (4)(-7)? 0=
Solution: (1)(-5)? (-6)=+(5? 6)=+30=30
Please follow the above steps to calculate (2), (3) and (4).
(2)(-5)? 6 = =
(3)(-6)? (-0.45)= =
(4)(-7)? 0=
Let's summarize the solution steps:
When two numbers are multiplied, the product must be determined first, and then the product must be determined.
Hebei education printing plate seventh grade mathematics first volume teaching plan 2
Consolidation exercise
1. Let's see who's better in the group verbal contest.
( 1)3? (-4) (2)2? (-6) (3)(-6)? 2
(4)6? (-2) (5)(-6)? 0 (6)0? (-6)
2. Calculate carefully. Note the sign and absolute value of the product.
( 1)(-4)? 0.25 (2)(-0.5)? (-2) (3)
(4)(-2)? (-
3. Use positive numbers and negative numbers to indicate the change of temperature, with the increase being positive and the decrease being negative.
When the mountaineering team climbs a mountain peak, the temperature changes by -6℃ every time it climbs 1 km. What will happen to the temperature after climbing 3 kilometers?
Five-minute customs clearance test
1. The following statement is wrong ()
A. A number multiplied by 0 still gets 0 b. A number multiplied by 1 still gets the original number 23? (-) 34 1534) (5)(-)? (-) (6)(-)? 5 26 10 15
C. If the product of two numbers is equal to 1, then the two numbers are opposite.
D. Multiply a number by-1 to get the reciprocal of the original number.
2. In the four numbers -2, 3, 4 and -5, any two numbers are multiplied, and the largest product is ().
A.10b.12c.-20 d. is not the answer above.
3. Calculate the following questions:
( 1)(- 10)? (-9)= (2)(-9)? (- 10)= ; (3)9? (-2)= ; (4)(-2)? 9 = ; (5)(-6)? (-5)= ; (6)(-5)? (-6)=
Fourth, experience association:
What are the calculation steps of 1. rational number multiplication? 2. What is the multiplication rule of rational numbers?
Five, homework exercises 1, 3.
Hebei education printing plate seventh grade mathematics first volume teaching plan 3
2.8 Rational Number Multiplication (Lesson 1)
learning target
1. Knowledge objective:
Understand the rationality of rational number multiplication rule, master rational number multiplication rule, and skillfully use rational number multiplication rule for accurate operation.
2. Ability goal: to cultivate one's ability of observation, analysis, abstraction and generalization by exploring the variant of the problem. 3. Emotional goal: cultivate the spirit of positive thinking and exploration and form good study habits. The emphases and difficulties of learning.
Emphasis: the derivation and clever use of rational number multiplication algorithm.
Difficulties: the determination of product symbols in rational number multiplication.
learning process
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1. We have been exposed to multiplication in primary school, so what is multiplication?
The operation of finding several numbers is called multiplication.
Multiply a number by 0 to get it.
Please list some multiplication formulas you learned in primary school.