a)cách 1(3/4+1/6)x2/3 cách 2( 3/4+1/6)x2/3 b)cách 1(5/9-1/2)x3/4 cách 2(5/9-1/2)x3/4

`a)(3/4+1/6)xx2/3`

Cách 1:

`(3/4+1/6)xx2/3`

`=(18/24+4/24)xx2/3`

`=22/24xx2/3`

`=11/12xx2/3`

`=(11xx2)/(12xx3)`

`=22/36`

`=11/18`

Cách 2:

`(3/4+1/6)xx2/3`

`=3/4xx2/3+1/6xx2/3`

`=(3xx2)/(4xx3)+(1xx2)/(6xx3)`

`=6/12+2/18`

`=1/2+1/9`

`=9/18+2/18`

`=11/18`

`b(5/9-1/2)xx3/4`

Cách 1:

`(5/9-1/2)xx3/4`

`=(10/18-9/18)xx3/4`

`=1/18xx3/4`

`=(1xx3)/(18xx4)`

`=3/72`

`=1/24`

Cách 2:

`(5/9-1/2)xx3/4`

`=5/9xx3/4-1/2xx3/4`

`=(5xx3)/(9xx4)-(1xx3)/(2xx4)`

`=15/36-3/8`

`=5/12-3/8`

`=10/24-9/24`

`=1/24.`

Trả lời