... biÕt: a) x : 2, 5 = 0, 003 : 0, 75 : x = 20 : ( −3 ) Bµi 2: T×m x, y ∈ Q , biÕt: c) a ) : ( x − 1) = ( x − 1) : 9; c) 3x − 2 x − = ; 4 b) : 40 = 0, 25 : x 15 d) : ( −0, ) = x : b) : ( x − 1) = ( x ... ; n ) = = A B A 2, 55 1 ,7 1 ,7 2, 55 = C 0,9 0,6 B 1 ,7 2, 55 1 ,7 0,6 = D 2, 55 0,9 1 Tõ tØ lƯ thøc: : ( − 2 ,7 ) = − : 29 2 ta suy c¸c tØ lƯ thøc: 29 − 27 − 27 = = 1 A B 29 −6 −6 2 1 29 −6 ... 75 b) ( 0, 8) ( 0, 4) c) 21 5 ⋅ 21 5 ⋅ 38 = 3 = ⋅ 35 = ⋅ 24 3 = 1944 63 ⋅ 83 ⋅ ⋅ = ⋅ ( 0,4 ) = 310 ( 0, 4) = 32 = 80 0,4 810 + 410 410 ⋅ 21 0 + 410 410 (2 10 + 1) 410 (4 + 1) = 4 = = = 4 = 81 d) 11...