a, (-8)-(-12-8)=(-8)+12+8= [(-8)+8}]+12= 0+12=12

b, 1765-(312+1765)= 1765-312-1765=(1765-1765)-312=0-312=-312

c. (31-12)-(46+31-12)= 31-12+46-31+12= (31-31)+(12-12)+46=0+0+46=46

d, (5674-97)-5674=5674-97-5674=(5674-5674)-97=0-97=-97

e, (-1075)-(29-1075)=(-1075)+29+1075=[(-1075)+1075]+29=0+29=29

g, (18+29)+(158-18-29)=18+29+158-18-29=(18-18)+(29-29)+158=0+0+158=158

h, (13-135+49)-(13+49)=13-135+49-13-49=(13-13)+(49-49)-135=0+0-149=0-149=-149

1a: 16

1. Tính tổng

a) ( - 24 ) + 6 + 10 +24

= [ ( -24 ) + 24 ] + ( 6 + 10)

= 0 + 16

= 16

b) 15 + 23 + ( - 25 ) + ( - 23 )

= (15 + 25 ) + [23 + ( -23 ) ]

= 40 + 0

= 40

c) ( - 3 ) + ( - 350 ) + ( - 7 ) + 350

= [ ( -3 ) + ( -7 ) ] + [ ( -350 ) + 350 ]

= -10 + 0

= -10

d)  ( - 9 ) + ( - 11 ) + 21 + ( - 1 )

= [ (-9) + (-1) ] + [ (-11) + 21 ]

= -10 + 10

= 0

2. Đơn giản biểu thức 

a) x + 25 + ( - 17 ) + 63

= x + ( 25 - 17 + 63 )

= x + 71

b)  ( - 75 ) - ( p + 20 ) + 95

= -75 - p - 20 + 95

= ( -75 - 20 + 95 ) - p

= 0 - p

= -p

3. Tính nhanh các tổng sau

a) ( 5674 - 97 ) - 5674

= 5674 - 94 - 5674

= ( 5674 - 5674 ) -94

= 0 - 94

= -94

b) (- 1075 ) - ( 29 - 1075 )

=-1075 - 29 + 1075

= ( -1075 + 1075 ) - 29

= 0 - 29

= -29

4. Bỏ dấu ngoặc rồi tính 

a )  ( 18 + 29 ) + ( 158 - 18 - 29 )

= 18 + 29 + 158 - 18 - 29

= ( 18 - 18 ) + ( 29 - 29 ) + 158

= 0 + 0 + 158

= 158

b )   ( 13 - 135 + 49 ) - ( 13 + 49 )

= 13 - 135 + 49 - 13 - 49

= ( 13 - 13 ) + ( 49 - 49 ) - 135

= 0 + 0 - 135

= -135

a)(-24)+6+10+24

=0+6+10

=16

b)15+23+(-25)+(-23)

=0+0

=0

c)(-3)+(-350)+(-7)+350

=0+(-3)+(-7)

=0

Bài 89: Tính tổng :

a) (-24) + 6 + 10 + 24 = 16

b) 15 +23+( -25) +(-23) = -10

c) (-3) + ( -350 ) + (-7) + 350 = -10

d) ( -9 ) + ( -11 ) + 21 + ( -1) = 0

Bài 90: Đơn giản biểu thức:

a) x + 25 + ( -17 ) + 63 = x + 71

b) ( -75) – (p + 20 ) + 95 = -p

Bài 91: Tính nhanh các tổng sau:

a) (5674 – 97) – 5674 = 5674 - 97 - 5674 = -97

b) (-1075 ) – ( 29 – 1075 ) = -1075 - 29 + 1075 = -29

Bài 92: Bỏ dấu ngoặc rồi tính:

a) (18 +29 ) + ( 158 – 18 – 29 ) = 18 + 29 + 158 - 18 - 29 = 158

b) ( 13 – 135 + 49 ) – ( 13 +49) = 13 - 135 + 49 - 13 - 49 = - 135

Bài 92 ; a . (18+29)+(158-18-29) b . (13-135+49)-(13+49) = 18+29+158-18-29 = 13- 135+ 49 -13-49 = (-18+18)+(-29+29)+158 = (-13-13) + 49)-135 = 0 + 0 +158 = 0 + 0 -135 = 158 = -135

a: \(\left(2345+45\right)-2345\)

\(=2345+45-2345\)

\(=45+\left(2345-2345\right)\)

=45+0

=45

b: \(\left(-2010\right)-\left(119-2010\right)\)

\(=-2010-119+2010\)

\(=\left(-2010+2010\right)-119\)

=0-119

=-119

c: \(\left(18+29\right)+\left(158-18-29\right)\)

\(=18+29+158-18-29\)

\(=158+\left(18-18\right)+\left(29-29\right)\)

=158+0+0

=158

d: \(126+\left(-20\right)+2004+\left(-106\right)\)

\(=126-20+2004-106\)

\(=\left(126-20-106\right)+2004\)

=0+2004

=2004

e: \(\left(-199\right)+\left(-200\right)+\left(201\right)\)

\(=-199-200+201\)

\(=-199+\left(201-200\right)\)

=-199+1

=-198

f: \(99+\left(-100\right)+101\)

\(=\left(99+101\right)-100\)

=200-100

=100

g: \(217+\left[43+\left(-217\right)+\left(-23\right)\right]\)

\(=217+43-217-23\)

\(=\left(217-217\right)+\left(43-23\right)\)

=0+20

=20

a) (2345-45)+2345

= 2300 + 2345

= 4645

b) (-2010)-(119-2010)

= -2010-119+2010

= (2010-2010)-199

= -199 

c) (18+29)+(158-18-29)

= 18+29+158-18-29

= (18-18)+(29-29)+158

= 158

d) 126+(-20)+2004+(-106)

= 126 -20 + 2004 - 106

= (126-20-106) +2004

= 2004

e) (-199)+(-200)+(-201)

= -(199+200+201)

= -600

g) 217+ [43+(-217)+(-23)]

= 217+ 43 - 217 + 23

= (217-217)+(43-23)

= 20

-Học tốt-

a: (-17)+5+8+17

\(=\left(-17+17\right)+\left(5+8\right)\)

=0+13

=13

b: \(\left(-24\right)+6+10+24\)

\(=\left(-24+24\right)+\left(6+10\right)\)

=0+16

=16

c: \(\left(-24\right)+6+\left(-10\right)+24\)

\(=\left(-24+24\right)+\left(6-10\right)\)

=0+(-4)

=-4

d: \(\left(-456\right)+2021-544\)

\(=2021-\left(456+544\right)\)

=2021-1000

=1021

e: \(\left(-1075\right)-29-\left(-1075\right)\)

\(=-1075+1075-29\)

=0-29

=-29

f: \(\left(-135\right)+48+140-\left(-5\right)\)

\(=48+\left(-135+140+5\right)\)

=48+10

=58

g: \(329+64+\left(-394\right)+36\)

\(=\left(329-394\right)+\left(64+36\right)\)

=100-65

=35

h: \(\left(-427\right)+\left(-123\right)+23+27\)

\(=\left(-427+27\right)+\left(-123+23\right)\)

=-400-100

=-500