Giúp mình với vote 5 sao 1.Tìm x biết a. 4.(18-5x)-12(3x-7)=15(2x-16)-6(x+14) b. 2(5x-8)-3(4x-5)=4(3x-4)+11

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1. Đáp án: $a$) $x=6$

                 $b$) `x = 2/7`

   Giải thích các bước giải:

   $1$.

   $a$, `4.(18-5x)-12(3x-7)=15(2x-16)-6(x+14)`

   `⇔ 72 – 20x – 36x + 84 = 30x – 240 – 6x – 84`

   `⇔ 72 + 84 + 84 + 240 = 30x-6x + 36x + 20x`

   `⇔ 480 = 80x`

   `⇔ x = 6`

     Vậy $x=6$

   $b$, `2(5x-8)-3(4x-5)=4(3x-4)+11`

   `⇔ 10x – 16 – 12x + 15 = 12x – 16 + 11`

   `⇔ 10x – 12x – 12x = -16 + 11 – 15 + 16`

   `⇔ -14x = -4`

   `⇔ x = 2/7`

      Vậy `x=2/7`

   Trả lời

2. Bài lm nek

   Nhớ vote cho mk 5 sao nhá ????

   Câu a.

   4 (18 – 5x) – 12 (3x – 7) = 15 (2x – 16) – 6 (x + 14)

   -> (72 – 20x) – (36x – 84) = (30x – 240) – (6x + 84)

   -> 72 – 20x – 36x + 84 = 30x – 240 – 6x – 84

   -> (72 + 84) + (-20x – 36x) = (30x – 6x) + (-240 – 84)

   -> 156 – 56x = 24x – 324

   -> 156 + 324 = 24x + 56x

   -> 80x = 480

   -> x = 480/80

   -> x = 6

   Câu b.

   2 (5x – 8) – 3 (4x – 5) = 4 (3x – 4) + 11

   -> (10x – 16) – (12x – 15) = (12x – 16) + 11

   -> 10x – 16 – 12x + 15 = 12x – 16 + 11

   -> (15 – 16) + (10x – 12x) = 12x – 5

   -> -1 – 2x = 12x – 5

   -> -1 + 5 = 12x + 2x

   -> 14x = 4

   -> x = 4/14

   -> x = 2/7

   Trả lời