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a)9.11.53+33.66.3+99
=99.53+99.66+99.1
=99(53+66+1)
=99.120
=11800
![](https://rs.olm.vn/images/avt/0.png?1311)
a ,[64+36]+[469+31]
=100+500
=600
b,[25.4].2018
=100.2018
=201800
mk sợ bạn chờ lâu
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15 . 4 . 6 . 125 . 8
= 60 . 750 . 8
= 45000 . 8
= 360000
![](https://rs.olm.vn/images/avt/0.png?1311)
a, 13 + 105 - ( 18 - 8 )
= 13 + 105 - 10
= 118 - 10
= 108
b, ( 64 + 36 +115 ) - 200
= ( 100 + 115 ) - 200
= 215 - 200
= 15
Bài 1:
a)13+21.5-(198:11-8)
= 13+105-(10-8)
= 118-10
= 108.
b)(64+115+36)-25.8
= (100+115)-200
= 215-200
= 15.
Bài 2 :
a)75.8.15.3
= (75.15).8.3
= 1125.8.3
= 9000.3
= 27000.
b)15.6.4.125.8
= (15.6.4).(125.8)
= 360.1000
= 360000.
c)6+8+10+12+14+16+18
= (6+8+10)+(12+18)+(14+16)
= 24+30+30
= 84.
![](https://rs.olm.vn/images/avt/0.png?1311)
9 . 11 . 53 + 33 . 46 . 3 + 99
= 9 . 11 . 53 + 33 . 3 . 46 + 99
= 99 . 53 + 99 . 46 + 99
= 99 . ( 53 + 46 ) + 99
= 99 . 99 + 99
= 9801 + 99
= 9900
9 . 11 . 53 + 33 . 46 . 3 + 99
= 99 . 53 + 99 . 46 + 99
= 99 . (53 + 46) + 99
= 99 . 99 + 99
= 9801 + 99
= 9900.
![](https://rs.olm.vn/images/avt/0.png?1311)
\(15\cdot6\cdot4\cdot125\cdot8\)
\(=\left(15\cdot4\right)\cdot6\cdot\left(125\cdot8\right)\)
\(=60\cdot6\cdot1000\)
\(=60000\cdot6\)
\(=360000\)
15.6.4.125.8
= 3.5.2.3.4.(125.8)
= (5.2).3.3.4.1000
=10.36.1000
=360000
![](https://rs.olm.vn/images/avt/0.png?1311)
15.6.4.125.8
= (15.4.6).(125.8)
= (60.6).1000
= 360.1000
= 360 000
15.6.4.125.8
=(15.4.6).(125.8)
=(60.6).1000
=360.1000
=360000
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có: \(D=\dfrac{\left(n+1\right)!}{\left(n-1\right)!}-n\)
\(=\dfrac{1\cdot2\cdot...\cdot\left(n-1\right)\cdot n\cdot\left(n+1\right)}{1\cdot2\cdot...\cdot\left(n-1\right)}-n\)
\(=n\left(n+1\right)-n\)
\(=n^2\)
Bài 1:
d,9.11.53+33.66.3+99
=99(53+66+1)
=99.120
=11880
e,259.268-259.168
=259(268-168)
=259.100
=25900
f,15.6.4.125.8
=90.1000.4
=360000