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1: =66+34-73-27+99=99
2: =54-45+30-54-30+5=-40
3: =42-56+33-33+56-42=0
4: =50-47-50+18+47-18=0
5: =10-28+30-4=2-4+10=12-4=8
\(\text{1.-(-66)+34+(-73)-27+99}.\)
\(=66+34-73-27+99=100-100+99=-99.\)
\(\text{2.54-(45-30+54)-30+5}.\)
\(54-45+30-54-30+5=\left(54-54\right)+\left(-45+5\right)+\left(30-30\right)=-40.\)
\(\text{3.42-56+33-(33-56+42)}.\)
\(=42-56+33-33+56-42=\left(42-42\right)+\left(-56+56\right)+\left(33-33\right)=0.\)
\(\text{4.50-(47+50-18)+(47-18)}.\)
\(=50-47-50+18+47-18=\left(50-50\right)+\left(-47+47\right)+\left(18-18\right)=0.\)
\(\text{5.10-(28-30+4)}.\)
\(=10-28+30-4=10+30-20-8-4=20-12=8.\)
\(\text{6.-(-73)+(44-94+27)+94}.\)
\(=73+44-94+27+94=\left(73+27\right)+\left(-94+94\right)+44=100+44=144.\)
42 + 43 + 44 + 45 - 32 - 33 - 34 - 35
= (42 - 32)+(43 - 33)+(44 - 34)+(45 - 35)
= 10+10+10+10
= 40
(64+65+66+67+68) - (54+55+56+57+58)
= 64+65+66+67+68 - 54-55-56-57-58
= (64 - 54)+(65 - 55) +(66 - 56) + (67- 57) + (68 -58)
= 10+10+10+10+10
= 50
42-56+33-(33-56+42)
=42-56+33-33+56-42
=(42-42)+(33-33)+(-56+56)
=0+0+0
=0
Chúc bạn học tốt! ^-^
B2:tìm x biết
1)x+18=6-2x
<=> 3x=-12
<=> x= -4
2)17-x=7-6x
<=>5x=-10
<=>x=-2
3)x+15=20-4x
<=>5x=5
<=>x=1
4)7x-4=20+3x
<=> 4x=24
<=>x=6
5)-12+x=5x-20
<=>4x=8
<=>x=2
6)4x-18=x+27
<=>3x=45
<=>x=9
7) 2.(x-5)-3.(x+7)=14
<=>2x-10-3x-21=14
<=>-x=14+10+21=45
<=>x=-45
8)5.(x-6)-2.(x+3)=12
<=>5x-30-2x-6=12
<=>3x=48
<=>x=12
9)-7.(5-x)-2.(x-10)=15
<=>-35+7x-2x+20=15
<=>5x=30
<=>x=6
10)3. ( x - 4 ) - ( 8 - x )=12
<=>3x-12-8+x=12
<=>4x=32
<=>x=8
11)4.(x-5)-(x+7)=-19
<=>4x-20-x-7=-19
<=>3x=8
<=>x=8/3
12)7.(x-3)-5.(3-x)=11x-5
<=>7x-21-15+5x=11x-5
<=>x=31
b1:bỏ ngoặc rồi tinh hợp lí
1) -( -66)+34+(-73)-27+99=66+34-73-27+99 =100-100+99=99
2)54-(45-30+54)-30+5=54-45+30-54-30+5=-45+5=-40
3)42-56+33-(33-56+42)=42-56+33-33+56-42=0
4)50-(47+50-18)+(47-18)=50-47-50+18+47-18=0
5) |25-24-10|-(28-30+4)=9-28+30-4=39-32=7
6)-(-73)+(44-94+27)+94=73+44-94+27+94=100+44=144
7) (-33+180-75)-(180+25)=-33+180-75-180-25=-100-33=-133
8)120-(-92+120-18)-92=120+92-120+18=108
a) (3⁵ . 3⁷) : 3¹⁰ + 5 . 2⁴ - 7³ : 7
= 3¹² : 3¹⁰ + 5.16 - 7²
= 3² + 80 - 49
= 9 + 31
= 40
b) (7⁵ + 7⁹) . (5⁴ + 5⁶) . (3³.3 - 9²)
= (7⁵ + 7⁹) . (5⁴ + 5⁶) . (81 - 81)
= (7⁵ + 7⁹) . (5⁴ + 5⁶) . 0
= 0
1) 42/35 - [ 33/14 . 21/22 - ( 54/25 : 27/25 - 7/10 )]
= 42/35 - ( 9/4-13/10)
=42/35-19/20
=1/4
2) a) 5/21 . x/34 = 35/102
x/34=35/102 : 5/21
x/34=49/34
=> x=34
Vậy x=34
b) 15/x . 21/13 = 45/91
15/x=45/91 : 21/13
15/x=15/49
=> x=49
Vậy x=49
42-56+33-(33-56+42)
=42-56+33-33+56-42
=0
54-(45-30+54)-30+5
=54-45+30-54-30+5
=-40
\(=0\)
\(=-40\)
Hk tốt