bài 1.
1. -28+32-45-32+28+45-8
= (-28+28)+(32-32)+(45-45)-8
= 0+0+0-8
= - 8
2.42-56+33-(33-56+42)
= 42-56+33-33+56-42
= (42-42) +(56-56) +(33-33)
= 0+0+0
= 0
3.54-(45-30+54)-30+5
= 54-45+30-54-30+5
= (54-54) +(5-45)+(30-30)
= 0 + (-40) + 0
= -40
4.45-(1997-2005)+1997
=45 - 1997 +2005 + 1997
= (45+2005) +(1997-1997)
= 2050 + 0
= 2050
5.4567+(1234-4567)-4
= 4567 + 1234 - 4567 - 4
= (4567-4567) + (1234-4)
= 0 + 1230
= 1230
6.1579-(53+1579)-(-53)
= 1579-53-1579+53
= (1579-1579) + (53-53)
= 0 + 0
=0
7.2001-15+54-2001-54
= (2001-2001)+(54-54) - 15
= 0+0 - 15
= -15
8.13579-(14-53)+(-13579)
= 13579 - 14+53 - 13579
= (13579-13579) +(53-14)
= 0 + 39
= 39
9.14537-4+(5-14537)
= 14537-4+5-14537
= (14537-14537) + (5-4)
= 0 + 1
= 1
10.6-(5-5847)+5-5847
= 6-5+5847+5-5847
= 6+(5-5) + (5847-5847)
= 6+0+0
=6
bài 2.
1.|x|=5
=> x=5 hoặc x=-5
vậy x=5 hoặc x=-5
2.|x| = 5+7-10
=> |x| = 2
=> x=2 hoặc x=-2
vậy x=2 hoặc x= -2