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 30/10/2021 Bởi Melanie 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 ⇒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 Bình luận
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 Bình luận
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
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