Question

tính bằng cách thuận tiện.

a, 0,75 x 1/13 + 3/4 x 5/13 + 75% x 7/ 13

b, ( 1 + 3+ 5 + ... + 2021) x ( 2121 x 22 - 2222 x 21)

                                            đag vội làm giúp ik

                                                    cảm ơn

Answer 1

`a)0,75 xx 1/13 +3/4 xx 5/13 + 75% xx 7/13` 

`=  3/4 xx 1/13 + 3/4 xx 5/13 + 3/4 xx 7/13`

`= 3/4 xx (1/13 +5/13 +7/13)` 

`= 3/4 xx  13/13`

`= 3/4 xx 1`  

`= 3/4`

`b)(1+3+5+...+2021)×(2121×22−2222×21)`

`=(1+3+5+...+2021)×(21×101×22−22×101×21)`

`=(1+3+5+...+2021)×0`

`=0`

Answer 2

a, 0,75 x 1/13 + 3/4 x 5/13 + 75% x 7/13

`= 3/4 xx 1/13 + 3/4 xx 5/13 + 3/4 xx 7/13`

` = 3/4 xx ( 1/13 + 5/13 + 7/13)`

` = 3/4 xx 13/13`

` = 3/4 xx1`

`= 3/4`

 

 ( 1 + 3+ 5 + ... + 2021) x ( 2121 x 22 - 2222 x 21)

` = ( 1 + 3+ 5 + ... + 2021) xx (46662 - 46662)`

` =  ( 1 + 3+ 5 + ... + 2021) xx  0`

` = 0`