Tính nhanh (-5).4.2(-2).3.(-25) TÌm X x-105:3=-23 |x-8|+12=25

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1. Đáp án:

   `a,(-5).4.2.(-2).3.(-25)`

   `=[(-5).(-2)].[4.(-25)].3.2`

   `=10.(-100).6`

   `=-6000`

   `b,x-105:3=-23`

   `\to x-35=-23`

   `\to x=12`

   Vậy `x=12`

   `c,|x-8|+12=25`

   `\to|x-8|=13`

   `\to` \(\left[ \begin{array}{l}x-8=13\\x-8=-13\end{array} \right.\) `\to` \(\left[ \begin{array}{l}x=21\\x=-5\end{array} \right.\) 

   Vậy `x\in{-5;21}`

    

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2. ( -5 ) . 4 . 2 (-2) . 3 . ( -25 )

   = { ( -5 ) . 2 } . { (- 25)  . 4 } . { (-2) . 3 }

   = (-10 ) . ( -100 ) . (-6)

   =1000 . ( -6 ) 

   = -6000

   x – 105 : 3 = -23

   $\Rightarrow x – 35 = -23$

   $\Rightarrow x = -23 + 35$

   $\Rightarrow x = 12$

   Vậy : $x = 12 $

   | x – 8 |+12 = 25

   $\Rightarrow | x – 8 | = 25 – 12 $

   $\Rightarrow | x – 8 | = 13 $

   $\Rightarrow $\(\left[ \begin{array}{l}x-8 = 13\\x-8=-13\end{array} \right.\)

   $\Rightarrow $ \(\left[ \begin{array}{l}x=21\\x=-5\end{array} \right.\) 

   Vậy : \(\left[ \begin{array}{l}x=21\\x=-5\end{array} \right.\)

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