Bài 1: Thực hiện phép tính sau : a) -5/9 + 7/9 b ) 1/2 + -3/4 c ) 7/13 - ( 13/15 + 7/13 ) d ) 6/11 . 10/17 . + 5/11 + 6/11 . 7/17 e )-2/11 + -9/11 f ) 11/2 - -3/4 g ) 12/11 - -7/19 + 12/19 h ) -5/7 . 2/11 + -5/7 . 9/11 + 5/7 Giúp với ạ ! Nhanh + dễ hiểu + làm theo cách lớp 6 + đúng ! Sẽ cho hay nhất + 5 sao !

Đáp án:

``

`a)` `(-5)/9 + 7/9`

`= (-5+7)/9`

`= 2/9`

``

`b)` `1/2 + (-3)/4`

`= 2/4 -3/4`

`= (2-3)/4`

`=(-1)/4`

``

`c)` `7/13 - (13/15 +7/13)`

`= 7/13 - 13/15 -7/13`

`= ( 7/13 - 7/13 ) -13/15`

`= 0-13/15`

`= 13/15`

``

`d)` `6/11 . 10/17 + 5/11+6/11 . 7/17`

`= 6/11 . ( 10/17 + 7/17 ) + 5/11`

`= 6/11 . 17/17 + 5/11`

`= 6/11 . 1 + 5/11`

`= 6/11 + 5/11`

`= (6+5)/11`

`= 11/11`

``

`e)` `(-2)/11 + (-9)/11`

`= (-2)/11 -9 /11`

`= (-2-9)/11`

`= (-11)/11`

`=-1`

``

`f)` `11/2 - (-3)/4`

`= 22/4 + 3/4`

`= (22+3)/4`

`=25/4`

``

`g)` `12/11 - (-7)/19 + 12/19`

`= 12/11 + 7/19 + 12/19``

`= 12/11 + (7/19 +12/19)`

`= 12/11 + 19/19`

`= 12/11 + 1`

`= 12/11 + 11/11`

`=23/11`

``

`h)` `(-5)/7 . 2/11 +(-5)/7 . 9/11 + 5/7`

`= 5/7 . (-2)/11 + 5/7 . (-9)/11 + 5/7 . 1`

`= 5/7 . ( ( -2)/11 + (-9)/11 + 1)`

`= 5/7 . ( -1 +1)`

`= 5/7 . 0`

`= 5/7`