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Bài 1:
a.
$-12-(-46)=-12+46=46-12=34$
b.
$-(-8)-54=8-54=-(54-8)=-46$
c.
$-15-(-72)=-15+72=72-15=57$
Bài 2:
a. $(156-812)-(156-12)=156-812-156+12$
$=(156-156)-(812-12)=0-800=-800$
b.
$-(-72+83)-(72+17)=72-83-72-17=(72-72)-(83+17)$
$=0-100=-100$
c.
$-(-23-78)+(77-178)=23+78+77-178$
$=(23+77)-(178-78)=100-100=0$
d.
$(-213-156)-(-213+44)=-213-156+213-44=(-213+213)-(156+44)$
$=0-200=-200$
a)5.(-8).2.(-3)
=[5.(-2)].[(-8).(-3)]
=-10.24
=-240
b)(45-135+72)-(45+72)
=45-135+72-45-72
=(45-45)+(72-72)-135
=0+0-135
=-135
c)3.(-5)2.2+2.(-5)-20
=3.25.2+2(-5)-20
=75.2+(-10)-20
=150+(-30)
=120
d)86.(-46)+46.27-46.41
=86.(-1).46+46.27-46.41
=-86.46+46.27-46.41
=46(-86+27-41)
=46(-100)
-4600
e)34(15-10)-15(34-10)
=34.15-34.10-15.34+15.10
=(34.15-15.34)+(15.10-34.10)
=[34(15-15)]+[10(15-34)]
=34.0+10(-9)
=0+(-90)
=-90
Bài 1: Tính
a) (−14) + (− 28) = -42 b) ( −26) + 47= 21 c) 35 + (− 63) = -28
d) ( −8) +12 +( −24)= -20 e) ( −26)−27= -53 f) ( −35)− ( −105)=70
Bài 2: Tính hợp lý
a) 54 +(12+ 46)= 112 b) 157− (200+57) =-100
c) (− 34) [(− 34)+2020]=(-34)+1986=1952
d) 45− (137− 155)=63 e) 27− 8− 12− 7 =0
f) ( −72)+26 −28− 6 =-80
Bài 3:
a) 11 - (15 + 11) = x - (25 - 9)
=> 11 - 15 - 11 = x - 25 + 9
=> x = 9 - 25 + 15
=> x = -1
b) 2 - x = 17 - (-5)
=> 2 - x = 17 + 5
=> -x = 17 + 5 - 2
=> -x = 20
=> x = -20
c) x - 12 = (-9) - 15
=> x - 12 = -9 - 15
=> x = -9 - 15 + 12
=> x = -12
d) IxI - 7 = 9
=> IxI = 9 + 7
=> IxI = 16
=> x = 16 hay x = -16
e) 9 - 25 = (7 - x) - (25 + 7)
=> 9 - 25 = 7 - x - 25 - 7
=> x = 7 - 7 - 25 + 25 - 9
=> x = -9
Bài 4:
a) 25 . 46 + 54 . 25
= 25(46 + 54)
= 25.100
= 2500
b) 1200 : 25
= (25.48) : 25
= 25:25 . 48
= 1.48
= 48
c) 1356 - 998
= 1356 + 2 - 998 - 2
= 1358 - 1000
= 358
d) 117 + 57 - 17
= 117 - 17 + 57
= 100 + 57
= 157
Bài 5:
a) 34 . 315
= 34 + 15
= 319
b) 88 : 88
= 88 - 8
= 80
= 1
c) 100 - [120 - (15 - 5)2 ]
= 100 - (120 - 102)
= 100 - (120 - 100)
= 100 - 120 + 100
= 80
Bài 3 :
a, 11 - ( 15 + 11 ) = x - ( 25 - 9 )
11 - 26 = x - 16
- 15 = x - 16
x = - 15 + 16
x = 1
b, 2 - x = 17 - ( - 5 )
2 - x = 22
x = 2 - 22
x = - 20
c, x - 12 = - 9 - 15
x - 12 = - 24
x = - 24 + 12
x = - 12
d, | x | - 7 = 9
| x | = 9 + 7
| x | = 16
x = 16 hoặc - 16
e, 9 - 25 = ( 7 - x ) - ( 25 + 7 )
- 16 = 7 - x - 32
x = 7 - 32 + 16
x = - 9
Bài 4 :
25 x 46 + 54 x 25
= 25 x ( 46 + 54 )
= 25 x 100
= 2500
b, 1200 : 25
= 12 x 100 : 25
= 12 x 4
= 48
c, 1356 - 998
= 358
d, 117 + 57 - 17
= ( 117 - 17 ) + 57
= 100 + 57
= 157
Bài 5 :
a, 3^4 . 3^15
= 3^19
b, 8^8 : 8^8
= 1
c, 100 - [ 120 - ( 15 - 5 )^2 ]
= 100 - ( 120 - 100 )
= 100 - 20 = 80
bai 4 : a) = 2500
b)=48
c)=157
bai 5 : a)= 1162261467
b)=1
c)= 80
45-58+(-45)+(+58)-3=45-58-45+58-3=(45-45)+(58-58)-3=-3
(-57)-(-12)+3-(-57)=-57+12+3+57=(-57+57)+12+3=15
-(-24)-(-30)+(-24)-30+8=24+30-24-30+8=(24-24)+(30-30)+8=8
-(-12)+(+19)-(+12)+8-19=12+19-12+8-19=(12-12)+(19-19)+8=8
47-(-53)+(-47)-(+53)=47+53-47-53=(47-47)+(53-53)=0
-(+28)+32-(-28)+(-34)=-28+32+28-34=(-28+28)-(34-32)=-2
15-(+72)+(-15)+(+72)=15-72-15+72=(15-15)+(72-72)=0
20-(+46)+(-25)-(-46)=20-46-25+46=(20-25)+(46-46)=-5
28-(-32)+(-28)-32+5=28+32-28-32+5=(28-28)+(32-32)+5=5
-75+(-49)+(+75)+49-12=-75-49+75+49-12=(-75+75)+(49-49)-12=-12
\(...=45-58-45+58-3=-3\)
\(...=-57+12+3+57=15\)
\(...=24+30-24-30+8=8\)
\(...=12+19-12+8-19=8\)
\(...=47+53-47-53=0\)
\(...=-28+32+28-34=-2\)
\(...=15-72-15+72=0\)
\(...=20-46-25+46=-5\)
\(=...28+32-28-32+5=5\)
\(...=-75-49+75+49-12=-12\)