Đáp án `+` Giải thích các bước giải :

`----------`

`a)` `1011/2012 xx 20122012/20132013 xx 201320132013/201120112011`

`= 1011/2012 xx 2012/2013 xx 2013/2011`

`= (1011xx2012xx2013)/(2012xx2013xx2011)`

`= (1011xxcancel2012xxcancel2013)/(cancel2012xxcancel2013xx2011)`

`= 1011/2011`

`----------`

`b)` `1313/2121 xx 165165/143143 xx 424242/151515`

`= 13/21 xx 15/13 xx 14/5`

`= (13xx15xx14)/(21xx13xx5)`

`= (cancel13xx15xx14)/(21xxcancel13xx5)`

`= (15xx14)/(21xx5)`

`= (5xx3xx7xx2)/(7xx3xx5)`

`= (cancel5xxcancel3xxcancel7xx2)/(cancel7xxcancel3xxcancel5)`

`= 2`

`----------`

`c)` `(1/4 + 1/24 + 1/124)/(3/4 + 3/24 + 3/124)+(2/7+2/17+2/127)/(3/7+3/17+3/127)`

`=(1(1/4+1/24+1/124))/(3(1/4+1/24+1/124)) + (2(1/7+1/17+1/127))/(3(1/7+1/17+1/127)`

`= 1/3 + 2/3`

`= (1+2)/3`

`= 3/3 = 1`

`----------`

Đáp án:

Giải thích các bước giải:

 `a) 1011/2012 xx 20122012/20132013 xx 201320132013/201120112011`

`= 1011/2012 xx 2012/2013 xx 2013/2011`

`= (1011 xx 2012 xx 2013)/(2012 xx 2013 xx 2011)`

`= 1011/2011`

`b) 1313/2121 xx 165165/143143 xx 424242/151515`

`= 13/21 xx 165/143 xx 42/15`

`= 13/21 xx 15/13 xx 14/5`

`= (13 xx 15 xx 14)/(21 xx 13 xx 5)`

`= 2`

`c) (1/4 + 1/24 + 1/124)/(3/4 + 3/24 + 3/124) + (2/7 + 2/17 + 2/127)/(3/7 + 3/17 + 3/127)`

`= (1(1/4+1/24+1/124))/(3(1/4+1/24+1/124)) + (2(1/7+1/17+1/127))/(3(1/7+1/17+1/127))`

`= 1/3 + 2/3`

`= 3/3`

`=1`