Question

1. tìm x :   

   a) 2( x + 15 ) - 7 - x = 15 + 2x

   b) - ( x + 7 ) + 2( 5 -x ) = 4x + 15

Answer 1

a) 2(x + 15) - 7 - x = 15 + 2x

2x + 30 - 7 - x = 15 + 2x

2x - x - 2x = 15 - 30 + 7

-x = -8

x = 8

b) - (x + 7) + 2(5 - x) = 4x + 15

-x - 7 + 10 - 2x = 4x + 15

0x = 19

Vậy phương trình vô nghiệm

Answer 2

   a) 2( x + 15 ) - 7 - x = 15 + 2x

=> 2( x + 15 ) - 7 - x - 15 - 2x = 0

=> 2x + 30 - 7 - x - 15 - 2x = 0

=> -x + 8 = 0

=> -x =- 8 

=> x = 8

   b) - ( x + 7 ) + 2( 5 -x ) = 4x + 15

=> - x - 7 + 10 - 2x - 4x - 15 = 0

=> -7x - 12 = 0 

=> -7x = 12

=> \(x=-\frac{12}{7}\)