Bài 47: Tìm x, biết:
a) x - 7 = -5 b) 128 - 3 . ( x+4) = 23
c) [ (6x - 39) : 7 ] . 4 = 12 d)( x: 3 - 4) . 5 = 15
e)( 3x - 24 ) . 73 = 2 . 74 g) x - [ 42 + (-28)] = -8
Bài 48: Tìm số nguyên x, biết:
a) | x + 2| = 0 b) | x - 5| = |-7|
c) | x - 3 | = 7 - ( -2) d) ( 7 - x) - ( 25 + 7 ) = - 25
e) | x - 3| = |5| + | -7| g) 4 - ( 7 - x) = x - ( 13 -4)
a) x - 7 = -5
x = -5 + 7
x = 2
b) 128 - 3 . ( x + 4 ) = 23
-3 . ( x + 4 ) = 23 - 128
-3 . ( x + 4 ) = -105
x + 4 = -105 : (-3)
x + 4 = 35
x = 35 - 4
x = 31
c) [ ( 6x - 39 ) : 7 ] . 4 = 12
( 6x - 39) : 7 = 12 : 4
( 6x - 39 ) : 7 = 3
6x - 39 = 3 . 7
6x - 39 = 21
6x = 21 + 39
6x = 60
x = 60 : 6
x = 10
d) ( x : 3 - 4 ) . 5 = 15
x : 3 - 4 = 15 : 5
x : 3 - 4 = 3
x : 3 = 3 + 4
x : 3 = 7
x = 7 .3
x = 21