16) x2.(x – 7) = 0 17) 9x.( – 7 – x) = 0 18) 5.( – 4).x = 100 19) (– 1).( – 3).( – 6).2.x = 72 20) x + (– 31) – (– 42) – (– 8) = – 54 21) x + 2x + x + 91 = – 5 22) – 152 – (3x + 1) = (– 2).( – 27) 23) x + x + x + 81 = – 3 – x 24) (– 13) – (13 – x) = – 16 – (– 17) 25) – (x – 6 + 85) = (x + 51) – 54 26) – (38 – x) – (37 – x) = 30 – x 27) 15 – (13 + x) = x – (24 – 18)

`16) x^2(x - 7) = 0`

`=> [(x^2=0),(x-7=0):}`

`=> [(x=0),(x=7):}`

Vậy `x in {0;7}`

`17) 9x(-7 - x) = 0`

`=> [(9x=0),(-7-x=0):}`

`=> [(x=0),(x=-7):}`

Vậy `x in {0;-7}`

`18) 5.(-4)x = 100`

`=> -20x = 100`

`=> x = 100 : (-20)`

`=> x = -5`

Vậy `x = -5`

`19) (-1). (-3). (-6). 2x = 72`

`=> -36x = 72`

`=> x = 72 : (-36)`

`=> x = -2`

Vậy `x = -2`

`20) x + (-31) - (-42) - (-8) = -54`

`=> x - 31 + 42 + 8 = -54`

`=> x = -54 + 31 - 42 - 8`

`=> x = -73`

Vậy `x = -73`

`21) x + 2x + x + 91 = -5`

`=> 4x + 91 = -5`

`=> 4x = -5 - 91`

`=> 4x = -96`

`=> x = -24`

Vậy `x = -24`

`22) -152 - (3x + 1) = (-2). (-27)`

`=> -152 - (3x+1) = 54`

`=> 3x + 1 = -152 - 54`

`=> 3x = -206`

`=> 3x = -207`

`=> x = -69`

Vậy `x = -69`

`23) x + x + x + 81 = -3 - x`

`=> 3x + 81 = -3 - x`

`=> 3x + x = -3 - 81`

`=> 4x = -84`

`=> x = -21`

Vậy `x = -21`

`24) (-13) - (13 - x) = -16 - (-17)`

`=> (-13) - 13 + x = 1`

`=> -26 + x = 1`

`=> x = 1+26 = 27`

Vậy `x = 27`

`25) -(x - 6+85) = (x+51) - 54`

`=> -x + 6 - 85 = x + 51 - 54`

`=> -x - x = 51 - 54 - 6 + 85`

`=> -2x = 76`

`=> x = -38`

Vậy `x = -38`

`26) -(38 - x) - (37 - x) = 30 - x`

`=> -38 + x - 37 + x = 30 - x`

`=> x + x + x = 30 + 38 + 37`

`=> 3x = 105`

`=> x = 35`

`27) 15 - (13+x) = x - (24 - 18)`

`=> 15 - 13 - x = x - 24 + 18`

`=> -x - x = -24 + 18 - 15 + 13`

`=> -2x = -8`

`=> x = 4`

Vậy `x = 4`

`@Chyn`