Tưởng of;-;

`2)2/3=(2xx6)/(3xx6)=12/18`

`7/9=(7xx7)/(9xx7)=49/63`

`6/5=(6xx3)/(5xx3)=18/15`

`2/3=(2xx5)/(3xx5)=10/15`

`5/9=(5xx5)/(9xx5)=25/45`

`49/56=(49:7)/(56:7)=7/8`

`6/8=(6xx7)/(8xx7)=42/56`

`2/9=(2xx7)/(9xx7)=14/63`

`49/56=(49:7)/(56:7)=7/8`

`1)1/2:2/3 .... 2/3 : 1/2`

`=>1/2xx3/2 .... 2/3xx2`

`=>3/4 .... 4/3`

Vì `3/4 < 1` và `4/3>1` 

`=>3/4<4/3`

__

`4/7:2/5 ... 4/7 : 3/5`

`=>4/7xx5/2....4/7xx5/3`

`=>20/14...20/21`

`=>10/7...20/21`

Vì `10/7>1` và `20/21<1` 

`=>10/7>20/21`

__

`4/15:4/7....2/5xx10/3`

`=>4/15xx7/4...20/15`

`=>7/15...20/15`

Vì `7<20` nên `7/15<20/15`

__

`5/6...15/18-11/18`

`=>5/6...4/18`

Ta có : MSC : `18`

`5/6 = 15/18`

Vì `15>4` nên `5/6 > 4/18`

`1/2:3/4+5/6:3/4-2/8:3/4`

`=1/2 xx 4/3 + 5/6 xx 4/3 - 2/8 xx 4/3`

`=4/3 xx ( 1/2 + 5/6 - 2/8)`

`=4/3 xx ( 1/2 + 5/6 - 1/4 )`

`=4/3 xx ( 6/12 + 10/12 - 3/12)`

`=4/3 xx ( 16/12 - 3/12)`

`=4/3 xx 13/12`

`=13/9`

`1+2/3`

`=3/3+2/3`

`=5/3`

`3)a)x/8=9/12`

`=>12x=8.9`

`=>12x=72`

`=>x=72:12`

`=>x=6`

Vậy `x=6`

__

`b)10/19+3/19:x=1/2`

`=>3/19:x=1/2-10/19`

`=>3/19:x=19/38-20/38`

`=>3/19:x=-1/38`

`=>x=3/19:(-1/38)`

`=>x=3/19.(-38)`

`=>x=-114/19`

`=>x=-6`

Vậy `x=-6`

__

`c)12/17 - 3/17x = 12/17`

`=> 3/17x = 12/17 - 12/17`

`=> 3/17x = 0`

`=> x= 0 : 3/17`

`=> x =0`

Vậy `x=0`

__

`d)x-1/2x+1/5x=-26/5`

`=>1x-1/2x+1/5x=-26/5`

`=>2/2x-1/2x+1/5x=-26/5`

`=>1/2x+1/5x=-26/5`

`=>5/10x+2/10x=-26/5`

`=>7/10x=-26/5`

`=>x=-26/5:7/10`

`=>x=-26/5 . 10/7`

`=>x=-52/7`

Vậy `x=-52/7`

__

`l)(2x-4/3)-1 1/3 = -8/9`

`=>2x-4/3 = -8/9+4/3`

`=>2x-4/3= -8/9+12/3`

`=>2x-4/3=4/3`

`=>2x=4/3+4/3`

`=>2x=8/3`

`=>x=8/3:2`

`=>x=8/3 . 1/2`

`=>x=8/6`

`=>x=4/3`

Vậy `x=4/3`

__

`g)(x-1/5)(x+3/4)=0`

`=>x-1/5=0` hoặc `x+3/4=0`

`=>x=0+1/5` hoặc `x=0-3/4`

`=>x=1/5` hoặc `x=-3/4`

Vậy `x in{1/5;-3/4}`

Tuổi già sức íu rồi nên cày đc mấy bài dài dài để tụi nó ko tranh th =)) _{với lại còn đc 2GP nữa hhee}

Như chắc là ko hợp với mấy chiến thần trong bócc toán đou :"))