7.(x-9)-5.(6-x)=-6=11.x
10.(x-7)-8.(x+5)=6.(-5)+124
-3
7.(x-9)-5.(6-x)=-6=11.x
10.(x-7)-8.(x+5)=6.(-5)+124
-3
By Samantha
By Samantha
#KhanhHuyen2006 – Xin câu trả lời hay nhất
`1) 7 . (x – 9) – 5 . (6 – x) = -6 + 11x`
`-> 7x – 49 – 30 – 5x = -6 + 11x`
`-> 7x + 5x – 11x = 63 + 30 – 6`
`-> x = 87`
`2) 10 (x – 7) – 8 (x + 5) = 6 . (-5) + 124`
`-> 10x – 70 – 8x + 40 = 94`
`-> 10x – 8x = 70 + 40 + 94`
`-> 2x = 204`
`-> x = 102`
`3) -3 < x – 1 ≤ -2 (x ∈ Z)`
`-> x – 1 ∈ {-2; -1; 0; 1; 2}`
`-> x ∈ {-1;0;1;2;3}`
`4) 2 ≤ |x – 5| < 5 (x ∈ Z)`
`-> |x – 5| ∈ {2;3;4}`
`-> x – 5 ∈ {±2; ±3; ±4}`
`-> x ∈ {1;2;3 ;7;8;9}`
Đáp án + Giải thích các bước giải:
`7.(x-9)-5.(6-x)=-6+11.x`
`→7x-63-30+5x=-6+11x`
`→7x+5x-11x=63+30-6`
`→x=87`
`———-`
`10.(x-7)-8.(x+5)=6.(-5)+124`
`→10x-70-8x-40=-30+124`
`->10x-8x=70+40-30+124`
`->2x=204`
`->x=102`
`———`
Bổ sung đề : Tìm `x∈Z`
`-3<x-1≤2`
Mà `x-1∈Z`
`→x-1∈{-2;-1;0;1;2}`
`→x∈{-1;0;1;2;3}`
`———-`
`2≤|x-5|<5`
Mà `|x-5|∈Z`
`→|x-5|∈{2;3;4}`
`→x-5∈{±2;±3;±4}`
`→x∈{3;2;1;7;8;9}`