Đáp án+Giải thích các bước giải:
Bài 1:
`a)(15xx1717)/(17xx1515)`
`=(15xx17xx101)/(17xx15xx101)`
`=(15xx17xx101)/(15xx17xx101)`
`=1`
`b)(1212xx131313)/(1313xx121212)`
`=(12xx101xx13xx10101)/(13xx101xx12xx10101)`
`=(12xx13xx101xx10101)/(12xx13xx101xx10101)`
`=1`
Bài 2:
`a)2019/2020` và `20192019/20202020`
Ta có: `20192019/20202020=(2019xx10001)/(2020xx10001)=2019/2020`
`->2019/2020=20192019/20202020`
Vậy `2019/2020=20192019/20202020`
`b)1234/2468` và `121212/242424`
Ta có:
`1234/2468=1234/(2xx1234)=1/2`
`121212/242424=(12xx10101)/(24xx10101)=12/24=1/2`
`->1234/2468=121212/242424`
Vậy `1234/2468=121212/242424`