( 3x/7 + 1 ) : (-4 ) = -1/28
3x/7 + 1 = -1/28 x (-4 )
(3x/7 + 1 = 1/7
3x/7 = 1/7 - 1
3x/7 = -6/7
Suy ra 3x = -6
x = -6 : 3
x = -2
=>3x/7+1=-1/28x(-4)
=>3x/7+1=1/7
=>3x/7=1/7-1
=>3x/7=-6/7
=>3x=6
=>x=6:3=2
k mình đi
Ta có : (3x/7+1) : (-4) = -1/28
3x/7+1 = -1/28 . (-4)
3x/8 = 1/7
Do đó 3x.7/56 = 8/56
Suy ra 3x.7=8
Suy ra 3x =8 : 7
Suy ra 3x = 8/7
Suy ra x = 8/7 : 3
Do đó x = 8/21