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a) =(53+47)*34-(53-47)*21=100x34-6x21=3400-126=3274
b)=(100-2)*2+1-(97+1)/2-1=197-50=147
chon cho minh nhe ban
![](https://rs.olm.vn/images/avt/0.png?1311)
53 x 39 + 47 x 39 - 53 x 21 - 47 x 21
= 39 x ( 53 + 47 ) - 21 x ( 53 + 47 )
= 39 x 100 - 21 x 100
= 100 x ( 39 - 21 )
= 100 x 18
= 1800
53 x 39 + 47 x 39 - 53 x 21 - 47 x 21
= 39 x ( 53 + 47 ) - 21 x ( 53 + 47 )
= 39 x 100 - 21 x 100
= 100 x ( 39 - 21 )
= 100 x 18
= 1800
ai k mik k lai
![](https://rs.olm.vn/images/avt/0.png?1311)
53 .39 + 47 . 39 - 53 . 21 - 47 .21
= (53 + 47) . 39 - (53 + 47) . 21
= 100 . 39 - 100 . 21
= 100 . (39 - 21)
= 100 . 18
= 1800
![](https://rs.olm.vn/images/avt/0.png?1311)
53*39+47*39-53*21-47*21
\(=39x\left(53+47\right)-\left(21x\left(53+47\right)\right)\)
\(=39x100-21x100\)
\(=100x\left(39-21\right)\)
\(=18x100=1800\)
![](https://rs.olm.vn/images/avt/0.png?1311)
b, 53.39 + 47.39 - 53.21 - 47.21
= 39( 53 + 47) - 21 53 + 47)
= 39.100 - 21.100
= 100(39 - 21)
= 100. 18
= 1800
bấm cho mình đúng nha ^_^
a)=78.(31+24+17)+22.72
=72.(78+22)
=72.100
=7200
b)=39.(53+47)-21.(53+47)
=100.(39-21)
=100.18
=1800
![](https://rs.olm.vn/images/avt/0.png?1311)
sửa chỗ sai của bạn lại: 53.39+47.39-53.21-47.21
= (53+47).(39-21)
=100.18
=1800
![](https://rs.olm.vn/images/avt/0.png?1311)
53 . 39 + 47 . 39 - 53 . 4 - 47 . 21
=53.(39-4)+47.(39-21)
=53.35+47.18
=1855+846
=2701
tich dung cho minh nhe
![](https://rs.olm.vn/images/avt/0.png?1311)
53x39+47x39-53x21-47x21
=39x ( 53+47) - 21x(53+47)
=39 x100 - 21x100
= 100x(39-21)
=100x18
=1800
2x53x12 +4x6x87 - 3x8x40
= (2x12)x53 + (4x16)x87 - (3x8) x40
= 24x53 + 24x87 + 24x40
= 24( 53+87+40)
= 24x180
=4320
=39*(53+47) - 21*(53-47)
=39*100 - 21*6
3900 - 126
=3774
đap số:3 774
ủng hộ nha