Thực hiện phép tính: 5² : (-5) + 4.{100-10².2.[2³-(10-3)]} Tìm x: a) 41 - 20 : x = 121, b) (3x- 9) (4+x)=0

Answer

$\bullet$ Thực hiện phép tính.

`5^2 : (-5) + 4 . {100 - 10^2 . 2 . [2^3 - (10 - 3)]}`

`= 25 : (-5) + 4 . {100 - 100 . 2 . [8 - (10 - 3)]}`

`= -5 + 4 . {100 - 200 . [8 - 7]}`

`= -5 + 4 . {100 - 200 . 1}`

`= -5 + 4 . {100 - 200}`

`= -5 + 4 . (-100)`

`= -5 - 400`

`= -405` 

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$\bullet$ Tìm `x:`

`a, 41 - 20 : x = 121`

`=> 20 : x = 41 - 121`

`=> 20 : x = -80`

`=> x = 20 : (-80)`

`=> x = {-1}/4`

Vậy `x = {-1}/4`

`b, (3x - 9) . (4 + x) = 0`

`=>` `[(3x - 9 = 0),(4 + x = 0):}`

`=>` `[(3x = 0 + 9),(x = 0 - 4):}`

`=>` `[(3x = 9),(x = - 4):}`

`=>` `[(x = 9 : 3),(x = - 4):}`

`=>` `[(x = 3),(x = - 4):}`

Vậy `x \in {3 ; -4}`