Tìm x ∈ Z , biết : a, 2x – 9 = -8-9 b, 35 – 5( x + 3 ) = |-15| c, -3 × | x – 1 | = – 27

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1. Đáp án+Giải thích các bước giải:

   $a, 2x – 9 = -8-9$

   $2x-9=-17$

   $2x=-17+9$

   $2x=-8$

   $x=-8:2$

   $x=-4$

   $b, 35 – 5( x + 3 ) = |-15|$

   $35-5(x+3)=15$

   $5(x+3)=35-15$

   $5(x+3)=20$

   $x+3=20:5$

   $x+3=4$

   $x=4-3$

   $x=1$

   $c, -3 × | x – 1 | = – 27$

   $|x-1|=-27:(-3)$

   $|x-1|=9$

   $<=>$\(\left[ \begin{array}{l}x-1=9\\x-1=-9\end{array} \right.\) $<=>$\(\left[ \begin{array}{l}x=9+1\\x=-9+1\end{array} \right.\) $<=>$\(\left[ \begin{array}{l}x=10\\x=-8\end{array} \right.\)

   $\text{Vậy x∈{10;-8}}$

    

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2. `#Xray`

   `a)2x-9=-8-9`

   `⇔2x=9-8-9`

   `⇔2x=-8`

   `⇔x=-4`

   Vậy `x=-4 `

   `b)35-5(x+3)=|-15|`

   `⇔35-5x-15=15`

   `⇔-5x=-36+15+15=-5`

   `⇔-5x=-5`

   `⇔x=1`

   Vậy `x=1`

   `c)  -3.|x-1|=-27`

   `⇔|x-1|=-27:(-3)=9`

   ⇔\(\left[ \begin{array}{l}x-1=9\\x-1=-9\end{array} \right.\) 

   ⇔\(\left[ \begin{array}{l}x=10\\x=-8\end{array} \right.\) 

   Vậy `x=10` hoặc `x=-8`

    

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