03[1]有理數(shù)乘法

1、有理數(shù)的乘法有理數(shù)的乘法劉輝劉輝4 4 7 73 3 0 05 5 2 2 7 76 6 9 9 0 0 4 428280 070700 0(-4)(-4) 7=? (-3)7=? (-3) (-9)=?(-9)=?-202462 3= 6-202-4-6 ( 2) 3= 6-202-4-6 2 ( 3)= 6-20246 ( 2) ( 3)= 60 ( 3) =0 ( 4) 0 =0 有理數(shù)乘法法則有理數(shù)乘法法則 兩數(shù)相乘，同號得正，異號兩數(shù)相乘，同號得正，異號得負，并把絕對值相乘得負，并把絕對值相乘. . 任何數(shù)同任何數(shù)同0 0相乘，都得相乘，都得0.0.2 3=6 (2) 3= 62 (

2、3)= 6 (2) (3)=6被乘數(shù)或乘數(shù)為被乘數(shù)或乘數(shù)為0時，結(jié)果是時，結(jié)果是0. .(1) 6 ( 9) (2) ( 6) ( 9)(3) ( 6) 9 (4) ( 6) 1(5) ( 6) ( 1) (6) 6 ( 1)(7) ( 6) 0 (8) 0 ( 6)(9) ( 6) 0.25 (10) ( 0.5) ( 8)計算：計算： 54 54 546 6 60 0 1.542 2 3 3 4 4 (5)(5)2 2 3 3 (4)(4) (5)(5)2 2 (3)(3) (4)(4) (5)(5)(2)(2) (3)(3) (4)(4) (5)(5)= 120= 120= 120= 1

3、20 幾個不等于零的數(shù)相乘，積的符號幾個不等于零的數(shù)相乘，積的符號由負因數(shù)的個數(shù)決定由負因數(shù)的個數(shù)決定. .當(dāng)負因數(shù)有奇數(shù)個當(dāng)負因數(shù)有奇數(shù)個時，積為負；當(dāng)負因數(shù)有偶數(shù)個時，積時，積為負；當(dāng)負因數(shù)有偶數(shù)個時，積為正為正. . 幾個數(shù)相乘，有一個因數(shù)為幾個數(shù)相乘，有一個因數(shù)為0，積就，積就為為0. .2 2 3 3 4 4 (5)(5)2 2 3 3 (4)(4) (5)(5)2 2 (3)(3) (4)(4) (5)(5)(2)(2) (3)(3) (4)(4) (5)(5)= 120= 120= 120= 120(4) (6) 3 (3)(5) 0.2 (7) (2) (4)解：原式解：原式=5 0.2 7 2 44 6 3 3= 216解：原式解：原式= 56 幾個不等于幾個不等于0的數(shù)相乘，積的符號由負因數(shù)的數(shù)相乘，積的符號由負因數(shù)的個數(shù)決定的個數(shù)決定. .當(dāng)負因數(shù)有奇數(shù)個時，積為負；當(dāng)當(dāng)負因數(shù)有奇數(shù)個時，積為負；當(dāng)負因數(shù)有偶數(shù)個時，積為正負因數(shù)有偶數(shù)個時，積為正. . 幾個數(shù)相乘，有一個因數(shù)為幾個數(shù)相乘，有一個因數(shù)為0，積就為，積就為0. . 有理數(shù)乘法法則有理數(shù)乘法法則 兩數(shù)相乘，同號得正，異號得負，