... +++++ 11 1 11 1 9 1 9 1 7 1 7 1 5 1 5 1 3 1 15 1 13 1 13 1 + (0,5đ) N= 15 4 15 1 2 1 = 2) Tìm x đợc 1 9 10 3 .30 3 10 :30 25 ,16 25 ,13 3 10 25 ,13 4 3 16 3 1 3 = = = = =+ x x x x x Bài 4 (1, 5đ) ... =- 71 b/ 1 ) = (12 6 +6)+7 -13 2 = (13 2 -13 2)+7=7 c/ 1 ) = 35-35 +12 6 =0 +12 6 =12 6 d /1 ) =- 515 -72+ 515 +32 =(- 515 + 515 )-(72-32) =0- 40 =-40 Bµi 3 :(3®) a /1 ) 4-(7+x)=x-9 7-x=4-(x-9) 7+x =13 -x 2x=6 x=3 b/ 1 ) ... a/ 5 1 12 5 25 − = − (0,5®) b/ 4 1 1.8 2 .1 56 .17 34.7 == (0,5®) c/ 5 1 6.5.4 )13 . (12 6.5.4 6.23 .12 = − = − (1 ) Bµi 4 (2®) Mçi ý ®óng cho 1 A=( 5 1 ) 7 3 7 3 − + − + (0,5®) A=0+ 5 1 5 1 − =...