Đáp án:
Giải thích các bước giải:
`a)``2/3>1/3`
`=>1/3>1/4`
`=>2/3>1/3>1/4`
`=>2/3>1/4`
Vậy `2/3>1/4`.
`b)``10>8`
`=>7/10<7/8`
Vậy `7/10<7/8`.
`c)``6/7>6/8=3/4`
`=>5>4=>3/5<3/4`
`=>6/7>3/4>3/5`
`=>6/7>3/5`
Vậy `6/7>3/5`.
`d)``14<21=2/3=4/6`
`=>60/72=5/6`
`=>4/6<5/6`
`=>14/21<60/72`
Vậy `14/21<60/72`.
`e)``38/133=2/7=1-5/7`
`=>129/344=3/8=1-5/8`
`=>5/7>5/8=>1-5/7<1-5/8`
`=>2/7<3/8`
`=>38/133<129/344`
Vậy `38/133<129/344`.
`f)``11/54<27/54=1/2`
`=>22/37>22/44=1/2`
`=>11/54<1/2<22/37`
`=>11/54<22/37`
Vậy `11/54<22/37`.
`g)``A=(10^1990+1)/(10^1991+1)`
`=>10A=(10.(10^1990+1))/(10^1991+1)`
`=>10A=(10^1991+10)/(10^1991+1)`
`=>10A=(10^1991+1+9)/(10^1991+1`
`=>10A=(10^1991+1)/(10^1991+1)+9/(10^1991+1`
`=>10A=1+9/(10^1991+1)`
`B=(10^1991+1)/(10^1992+1`
`=>10B=(10.(10^1991+1))/(10^1992+1`
`=>10B=(10^1992+10)/(10^1992+1`
`=>10B=(10^1992+1+9)/(10^1992+1`
`=>10B=(10^1992+1)/(10^1992+1)+9/(10^1992+1`
`=>9/(10^1991+1)>9/(10^1992+1)`
`=>1+9/(10^1991+1)>1+9/(10^1992+1`
`=>10A>10B`
`=>A>B`
Vậy `A>B`.
