Bài 1: Tìm x a. -1/3 × x – 1 = 2/5 b. 3/4 × x + 1/2 = -3/5 c. 3x – 1/7 = 1/14 – 1/21 d. -5 × |2x +3 |= -1/2

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1. Đáp án:

    

   Giải thích các bước giải:

    ` -1/3 . x – 1 = 2/5 `

   ` -1/3 . x = 2/5 + 1 `

   ` -1/3 . x = 7/5 `

   ` x = 7/5 : (-1)/3 `

   ` x = -21/5 `

   vậy ` x = -21/5 `

   ` 3/4 . x + 1/2 =-3/5 `

   ` 3/4 . x = -3/5 – 1/2 `

   ` 3/4 . x = -11/10 `

   ` x = -11/10 : 3/4 `

   ` x = -22/15 `

   vậy ` x = -22/15 `

   ` 3x -1/7 = 1/14 – 1/21 `

   ` 3x – 1/7 = 1/42 `

   ` 3x = 1/42 + 1/7 `

   ` 3x = 1/6 `

   ` x = 1/6 : 3 `

   ` x = 1/18 `

   vậy ` x = 1/18 `

   ` -5 . | 2x+3| = -1/2 `

   ` |2x+3| = -5 : (-1)/2 `

   ` |2x+3 | = 10 `

   ` 2x + 3 = 10 `

   ` 2x = 7 `

   ` x = 7:2`

   ` x = 7/2 `

   ` 2x+3 = – 10 `

   ` 2x = – 10 – 3 `

   ` 2x = -13 `

   ` x = -13 : 2 `

   ` x = -13/2 `

   vậy ` x \in{7/2;-13/2}`

   Trả lời

2. $#Dino$

   `a) -1/3.x-1=2/5`

   `⇒-1/3x=2/5+1=7/5`

   `⇒x=7/5:(-1)/3=-15/7`

   …………………….

   `b) 3/4.x+1/2=-3/5`

   `⇒3/4x=-3/5-1/2=-11/10`

   `⇒x=-11/10:3/4=-22/15`

   …………………………….

   `c) 3x-1/7=1/14-1/21`

   `⇒3x=1/7+1/14-1/21`

   `⇒3x=4/21`

   `⇒x=4/21:3=4/63`

   ………………………..

   `d) -5.|2x+3|=-1/2`

   `⇒|2x+3|=-1/2:(-5)=1/10`

   `1) 2x+3=1/10⇒x=-29/20`

   `2) 2x+3=-1/10⇒x=-1/14`

    

   Trả lời