Bài `1.`
`a)`
`(-7/12)` + `11/8` - `5/9`
= `(-56/96)` + `132/96` - `5/9`
= `76/96` - `5/9`
= `19/24` - `5/9`
= `171/216` - `120/216`
= `51/216`
= `17/72`
`b)`
`( 3/4 - 7/2) . ( 10/11 + 1/11)`
`= ( 6/8 - 28/8 ) . ( 11/11 )`
`= (-11/4) . 1`
`= ( -11/4 )`
`c)`
`1/7` . `2014^0` - `8/7` : `8-3` : `3/4` . `(-2)^2`
`= 1/7 . 1 - 1/7 - 4 . 4`
`= 1/7 - 1/7 - 16`
`= 16`
d)Ta có
`8/9 × 15/16 × 24/25 × ... × 2499/2500`
`= (2 × 4)/(3 × 3) × (3 × 5)/(4 × 4) × (4 × 6)/(5 × 5) × ... × (49.51)/(50.50)`
`= ( 2 × 3 × 4 × .... × 49 )/( 3 × 4 × 5 × ... ×50 )` × `( 4 × 5 × 6 × ... × 51 )/( 3 × 4 × 5 × ... ×50)`
`= 2/50 × 51/3`
`= 1/25 × 17`
`= 17/25`
Bài `2.`
`a)`
`x - 2/3 = 7/12`
`x = 7/12 +2/3`
`x = 5/4`
b)`11/12`.x+`3/4`=`-1/6`
`11/12 × x =`(-1/6) - 3/4`
`11/12` × x = (-11/12)`
`x = (-11/12) : 11/12`
`x = -1`
`c)`
`| x - 1/3 | = 5/6`
`⇒` `| x - 1/3 | = 5/6` hay `-5/6`
Ta chia làm `2` cách `:`
Cách `1 `:`
`x - 1/3 = 5/6`
`x = 5/6 + 1/3`
`x = 5/6 + 2/6`
`x = 7/6`
Cách `2` `:`
`x - 1/3 = -5/6`
`x = -5/6 + 1/3`
`x = -5/6 + 2/6`
`x = -3/6`
`x = -1/2`
Vậy `x = 7/6` hay `-1/2`
Bài `3:`
`a)`
`17/71 = 2397/10011`
`34/141 = 4794/10011`
`⇒` `2397/10011 < 4794/10011`
`→` `17/71 < 34/141`
`b)`
`51/56` và `61/66`
Ta có `:`
`51/56 = 3366/3696`
`61/66 = 3416/3696`
`⇒` `3366/3696 < 3416/3696`
`→` `51/56 < 61/66`
