Toán Lớp 6: 2(x – 5) – 3(x + 7) = 14 3(x – 4) – (8 – x) = 12 x – 12 – 25) = -8 175 – 5(x + 3) = 85

TRẢ LỜI

1. 2 ( x – 5 ) – 3 ( x + 7 ) = 14

   ⇔ 2x – 10 – 3x – 21 = 14

   ⇔ – x – 31 = 14

   ⇔ – x = 14 + 31

   ⇔ – x = 45

   ⇔ x = – 45

   Vậy x = – 45

   ———————————–

   3 ( x – 4 ) – ( 8 – x ) = 12

   ⇔ 3x – 12 – 8 + x = 12

   ⇔ 4x – 20 = 12

   ⇔ 4x = 12 + 20

   ⇔ 4x = 32

   ⇔ x = 8

   Vậy x = 8

   —————————————–

   x – ( 12 – 25 ) = – 8

   ⇔ x – 12 + 25 = – 8

   ⇔ x + 13 = – 8

   ⇔ x = – 8 – 13

   ⇔ x = – 21

   Vậy x = – 21

   ————————————

   175 – 5 ( x + 3 ) = 85

   ⇔ 175 – 5x – 15 = 85

   ⇔ 160 – 5x = 85

   ⇔ – 5x = 85 – 160

   ⇔ – 5x = – 75

   ⇔ x = ( – 75 ) : ( – 5 )

   ⇔ x = 15

   Vậy x = 15

   Trả lời
2. 2(x – 5) – 3(x + 7) = 14

   <=>2x-10-3x-21=14

   <=>2x-3x=14+10+21

   <=>-x=45

   <=>x=-45

   Vậy x=-45 

                                                                       

   3(x – 4) – (8 – x) = 12

   <=>3x-12-8+x=12

   <=>3x+x=12+12+8

   <=>4x=32

   <=>x=32:4=8

   Vậy x=8

                                                                       

   x-(12-15)=-8

   <=>x-12+15=-8

   <=>x+3=8

   <=>x=8-3=5

   Vậy x=5

                                                                       

   175 – 5(x + 3) = 85

   <=>175-5x-15=85

   <=>-5x=85+15-175

   <=>-5x=-75

   <=>x=15

   Vậy x=15

   Trả lời