bài giảng toán 6 quy đồng mẫu nhiều phân số

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T nhõn xet ú, ta cú thờ quy ng mu cỏc phõn sụ nay nh thờ nao ? Bi 28 (tr19) ap an: a) Mu chung : BCNN ( 16, 24, 56 ) =3 36 Quy ng mu : 3 3.21 63 = = 16 16. 21 3 36 5 5.14 70 = = 24 24.14 3 36 21 21 .6 1 26 = = 56 56. 6 3 36 ap an: Bi 28 (tr19) : 21 b) Phõn sụ cha tụi gian 56 Cú thờ giai gn hn bng cỏch rut gn cỏc 21 3 = phõn sụ trc khi quy ng mu : 56 8... ; = ; = = = 16 48 24 48 56 8 48 3 3.21 63 a) = = 16 16. 21 3 36 5 5.14 70 = = 24 24.14 3 36 21 21 .6 1 26 = = 56 56. 6 3 36 3 9 b) = ; 16 48 5 10 = 24 48 21 3 18 = = 56 8 48 HNG DN HOC NHA 1 Bi va hoc : - Hc thuục quy tc - Bai tõp nha : Bai 29, 30, 31 SGK (tr19) Hng dõn bi 30 SGK : a) Nhõn xet 120 la bụi cua 40 nờn lõy luụn 120 la mu chung 24 12 b) Nờn rut gn ri mi quy ng = 1 46 73 c) Sụ 60 nhõn 2 c 120,... Quy ụng mõu cac phõn sụ : 3 11 5 , , 44 18 36 ap an: ?3 b) Ta cú : 3 11 5 5 ; ; = 44 18 36 36 Mu chung : BCNN(44, 18, 36) = 3 96 3 3.9 27 = = 44 44.9 3 96 11 11.22 242 = = 18 18.22 3 96 5 5.11 55 = = 36 36. 11 3 96 Bi 29 (tr19) Quy ng mu cỏc phõn sụ sau : 3 5 a) va 8 27 ap an: Bi 29 (tr19) 3 3.27 81 a) ; = = 8 8.27 2 16 5 5.8 40 = = 27 27.8 2 16 Bi 28 (tr19) a) Quy ng mu cỏc phõn sụ sau : 3 5 21 , , 16. .. la mu chung 24 12 b) Nờn rut gn ri mi quy ng = 1 46 73 c) Sụ 60 nhõn 2 c 120, sụ nay chia hờt cho 30 va 40 nờn nú chinh la mu chung 64 d) Khụng nờn rut gn ma nhõn xet rng 90 90 2 = 180 chia hờt cho 60 va 18 nờn 180 chinh la mu chung HNG DN HOC NHA 2 Bi sp hoc : Tiờt 76 : Luyờn tõp - Xem trc cỏc bai tõp phõn luyờn tõp (SGK trang 19, 20) XIN CHâN THàNH CảM ơN Các thầy giáo, cô giáo và các em học . -+ 44 44 . . . . . . 56 7489:;8< 56 7489:;8< 8= 8=   -+ -+ >? >? 6 6 @7A-22(2 *6 @7A-22(2 *6 )- )- ( ( ( (   )(*) )(*) -+ -+   -+ -+ -+ - ) ( '( )  ' ) * '0- '0- *+ *+ '0 '0               &!2- &!2-     . ( ,+ ,+ ,+  -   ,+ - ,+ / ' '   = = - - &( &( )- 6 + )- 6 +  &&  + +  & 1 − − − 44 44 2%""/())*+&+1,- 2%""/())*+&+1,- 31 31 &( &( . − = − 4,/ 4,/ @?-1A9: 16 5"#$%""/ 5"#$%""/ , ,    ' 44 44 , , @?-1A9: 16 ' ' 