The eighth grade mathematics teaching plan Hunan Education Edition Volume 1 (1)
1.2 decimal multiplication and division method
1.2. 1 the multiplication and division of fractions
(Class 3)
Teaching objectives
1 The fractional multiplication and division method is obtained by analogy, and the fractional multiplication and division operation will be performed.
Understanding the concepts of reduction and simplest fraction will result in the reduction of scores.
Important and difficult
Emphasis: Fractional multiplication and division method and its application in calculation Difficulties: Calculation of fractional multiplication and division method
Eight Grade Mathematics Teaching Plan Volume I Hunan Education Edition (2)
teaching process
First, create situations and introduce new lessons.
1 Review of Fractional Multiplication and Division Method
2924 calculation: (1)? ; (2? What are the rules of fractional multiplication and division? 3 1039
2 analogy: change the above scores into component numbers: (1) Wisdom Fofo Agbo? ,? 2(u？ 0) How to calculate? gvgv
In this lesson, we will learn the multiplication and division of fractions (blackboard writing topic).
Second, cooperate and exchange, and explore new knowledge.
Law of multiplication and division of 1 fraction
( 1)fuf？ ufufvf？ v，？ 2? (u？ 0) gvg？ vgvgug？ u
Can you express the multiplication and division of fractions in words?
Fraction multiplied by fraction, numerator multiplied by numerator, denominator multiplied by denominator, respectively, as the numerator and denominator of the product, and then omit the common factor of numerator and denominator.
Fraction is divided by fraction, and numerator and denominator of divisor are multiplied by divisor in turn. Preliminary application of fractional multiplication and division, fractional and simplest fractional concepts
2x2y23x22x Example 1 Calculation:? 1? Students finish independently, teacher comments? 3; ? 25yxx？ 1x？ 1
Comments: (1) Fractional multiplication can multiply the numerator and denominator respectively and then subtract the common factor of the numerator and denominator, which is called divisor. A fraction whose numerator and denominator have no common factor is called simplest fraction.
(2) The division of fractions is actually the multiplication of fractions, which is reflected here. Transformation? The idea.
Third, application migration, integration and improvement.
1 Decimal multiplication and division method that requires factorization to reduce.
x？ 14x28x26x？ 2; (22? Example 2 Calculation: (1) 2xx? 1x？ 2x？ 1x？ 1
Comments: If the numerator and denominator contain polynomial factors, the factors should be decomposed first and then calculated according to the law. Simplification of Fractional Results and Its Significance
x2？ 9x2？ 4x？ 4; (2)2 cases and 3 simplification: (1)2 x? 6x？ 9x？ 2x
Comments: When performing fractional operation, it is generally necessary to simplify the results. Why simplify the result of the score?
Please complete the following questions first:
x2？ 9 cases 4 When x=5, find the value of 2. x？ 6x？ nine
Now you know why you want to simplify the result of the score? Simplifying the result of the score makes it easier to find the value of the score.
Eight Grade Mathematics Teaching Plan Hunan Education Edition Volume 1 (3)
Classroom practice, consolidate and improve
2x6y28x2y2131calculation:? 12; ? 26xy？ 3; (4)? x？ 2? x2？ 4x？ 4? 3yx32x？ 1x？ 2
xy？ 5xx2？ 2xy？ y2
2 Simplify: 1? 2 ; ? 2? y？ 10y？ 25y？ x
Is it right to make an appointment below? If not, point out the cause of the error and correct it.
? 1? 2x？ 2y2(x？ y) 1？ 122 x2 =； 2? 222222x+2y2(x？ y)x？ yx？ yx？ 3x？ three
x2？ 2x？ 1x？ 1? 2? The value of x, where x? 2005. "Some students used this question to put x=20094? Calculation: x2? 1x？ x
Miscopied as 2900? But his calculation result is correct. What do you think is going on?
Review and summarize, expand and improve
Homework: P 12 A group 1, 3 B 4
Postscript of teaching:
Hunan education edition eighth grade mathematics teaching plan volume I related articles;
1. The first volume of Grade 8 is the whole math teaching plan.
2. The first volume of the eighth grade mathematics teaching plan is the whole volume of PEP.
3. The first volume of the eighth grade mathematics teaching plan
4. The first volume of the eighth grade mathematics teaching plan is taught by people.
5. PEP version of the first volume of the eighth grade mathematics teaching plan