... ( 9, 17) .0,2 :: 2, 47. 0,5 ( 3,53).0, 50,2.( 20,83 9, 17) :: 0,5.(2, 47 3,53)0,2.( 30) : 0,5.66 : 3 2b − + −− −= − −+= −= − = −Bµi tËp 25 (tr16-SGK )a) 1 ,7 2,3x − = → x- 1 .7 = 2,3 ... thÞ sè tiỊn muaa) 5 kg gµ vµ 7 kg ganb) 2 kg gµ vµ 3 kg ganBiÕt r»ng, gi¸ gµ lµ x (®/kg); gi¸ ngan lµ y (®/kg)Bµi tËp 2: ghi néi dung bµi to¸n cã h×nh vÏ trang 36 - SGK.(häc sinh 1 lµm bµi ... biÕn.?33 3 33 3( ) (5 ) ( 7 )1 5 ( 7) xy xy xyxy xy+ + −= + + − = − Bµi tËp 16 (tr34-SGK)TÝnh tỉng 25xy2; 55xy2 vµ 75 xy2.(25 xy2) + (55 xy2) + (75 xy2) = 155 xy2IV....