nha hả bài hộnminhf Làm

Bài 1:

`a,3/5+4/15`

`= 9/15+4/15`

`=13/15`

`b,-3/5+5/7`

`= -21/35+25/35`

`= 4/35`

`c,5/6: (-7/12)`

`= 5/6 . 12/-7`

`= 60/-42`

`= 10/-7`

`d,-21/24: (-14/8)`

`= -7/8: (-7/4)`

`= -7/8 . 4/-7`

`= -1/2 . 1/-1`

`= 1/2`

`e,4/5: (-8/15)`

`= 4/5: 15/-8`

`= 1/1 . 3/-2`

`= 3/-2`

`f,3/5+ (-7/4)`

`= 12/20+ (-35/20)`

`= -23/20`

`g,5/12- (-7/6)`

`= 5/12+7/6`

`= 5/12+14/12`

`= 19/12`

`h,-15/16 . 8/-25`

`= 3/2 . 1/5`

`= 3/10`

Bài 2:

`a,6 4/5 - (1 2/3 + 3 4/5)`

`= 6 4/5 - 1 2/3 - 3 4/5`

`= 6 4/5 - 3 4/5 - 1 2/3`

`= 3 - 1 2/3`

`= 1 1/3`

`e,-3/5 . 5/7+ (-3/5).3/7 + (-3/5).6/7`

`= -3/5.(5/7+3/7+6/7)`

`= -3/5 . 14/7`

`= -3/5 . 2/1`

`= -6/5`

`f,1/3 . 4/5+1/3 . 6/5-4/3`

`= [1/3. (4/5+6/5)] - 4/3`

`= [1/3 . 10/5] - 4/3`

`= [1/3 . 2/1] - 4/3`

`= 2/3 - 4/3`

`= -2/3`

`g,4/19. (-3/7)+ (-3/7).15/19+5/7`

`= (4/19+15/19). (-3/7)+5/7`

`=19/19. (-3/7)+5/7`

`= 1. (-3/7)+5/7`

`= -3/7+5/7`

`= 2/7`

`h,5/9 . 7/13+5/9 . 9/13-5/9 . 3/13`

`= 5/9.(7.13+9/13-3/13)`

`= 5/9. 13/13`

`= 5/19. 1`

`= 5/19`

Xin hay nhất !