a. 2(x – 5) – 3(x + 7) = 14 b. 5(x – 6) – 2(x + 3) = 12 c. 3(x – 4) – (8 – x) = 12 d. -7(3x – 5) + 2(7x – 14) = 28

a. 2(x – 5) – 3(x + 7) = 14
b. 5(x – 6) – 2(x + 3) = 12
c. 3(x – 4) – (8 – x) = 12
d. -7(3x – 5) + 2(7x – 14) = 28

0 bình luận về “a. 2(x – 5) – 3(x + 7) = 14 b. 5(x – 6) – 2(x + 3) = 12 c. 3(x – 4) – (8 – x) = 12 d. -7(3x – 5) + 2(7x – 14) = 28”

  1. a. 2(x – 5) – 3(x + 7) = 14

    ⇒2x-10-3x-21=14

    ⇒-x=14+21+10

    ⇒-x=45

    ⇒x=-45

    Vậy x=-45

    b.5(x – 6) – 2(x + 3) = 12

    ⇒5x-30-2x-6=12

    ⇒3x=12+6+30

    ⇒3x=48

    ⇒x=16

    Vậy x=16

    c. 3(x – 4) – (8 – x) = 12

    ⇒3x-12-8+x=12

    ⇒4x=12+8+12

    ⇒4x=32

    ⇒x=8

    Vậy x=8

    d. -7(3x – 5) + 2(7x – 14) = 28

    ⇒-21x+35+14x-28=28

    ⇒-7x=28+28-35

    ⇒-7x=21

    ⇒x=-3

    Vậy x=-3

     

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  2. a, 2(x – 5) – 3(x + 7) = 14

    ⇔ 2x – 10 – 3x – 21 = 14

    ⇔ (2x – 3x) – (10 + 21) = 14

    ⇔ -x – 31 = 14

    ⇔ -x = 14 + 31

    ⇔ -x = 45

    ⇔ x = -45

    b, 5(x – 6) – 2(x + 3) = 12

    ⇔ 5x – 30 – 2x – 6 = 12

    ⇔ (5x – 2x) – (30 + 6) = 12

    ⇔ 3x – 36 = 12

    ⇔ 3x = 12 + 36

    ⇔ 3x = 48

    ⇔ x = 48 : 3

    ⇔ x = 16

    c, 3(x – 4) – (8 – x) = 12

    ⇔ 3x – 12 – 8 + x = 12

    ⇔ (3x + x) – (12 + 8) = 12

    ⇔ 4x – 20 = 12

    ⇔ 4x = 12 + 20

    ⇔ 4x = 32

    ⇔ x = 8

    d, -7(3x – 5) + 2(7x – 14) = 28

    ⇔ -21x + 35 + 14x – 28 = 28

    ⇔ (-21x + 14x) + (35 – 28) = 28

    ⇔ -7x + 7 = 28

    ⇔ -7x = 28 – 7

    ⇔ -7x = 21

    ⇔ x = 21 : (-7)

    ⇔ x = -3

     

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