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

Tính nhanh 

a) 78*31+78*24+78*17+22*72

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

1800 là kết quả đúng

53*39+47*39-53*21-47*21

\(=39x\left(53+47\right)-\left(21x\left(53+47\right)\right)\)

\(=39x100-21x100\)

\(=100x\left(39-21\right)\)

\(=18x100=1800\)

kết quả là 1800 nha bạ

\(53.39+47.39-53.21-47.21\)

\(=53\left(39-21\right)+47\left(39-21\right)\)

\(=\left(39-21\right)\left(53+47\right)\)

\(=18.100=1800\)

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

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

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.(39-4)+47.(39-21)

=53.35+47.18

=1855+846

=2701

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

= 39x( 53+47)-212-21

=39x100-212-21

=3900-212-21

=3667

53 .39 + 47 . 39 - 53 . 21 - 47 .21

= (53 + 47) . 39 - (53 + 47) . 21

= 100 . 39 - 100 . 21

= 100 . (39 - 21)

= 100 . 18

= 1800

53 . 39 + 47 . 39-53 .21 - 47 . 21

= 39. (53 + 47 ) - 21. ( 53 -47)

=39 . 100 - 21 . 6

= 3900 -126

=3774

\(53.39+47.39-53.21-47.21\)

\(=39.\left(47+53\right)-\left(53-47\right).21\)

\(=39.100-6.21\)

\(=3.13.100-2.3.21\)

\(=3.\left(1300-42\right)\)

\(=3.1258\)

\(=3774\)

=-175 bạn ạ

-175 nhé