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

Question

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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Raelynn 2 năm 2021-08-22T15:00:29+00:00 2 Answers 25 views 0

Answers ( )

  1. thienthanh
    0
    2021-08-22T15:01:46+00:00
    Reply

    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`

  2. baothah
    0
    2021-08-22T15:02:20+00:00
    Reply

    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

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