Trình bày lời giải:
Bài `5.`
`a)`
`x=2/3+(-6)/7`
`=>x=14/21-18/21`
`=>x=-4/21`
Vậy `x=-4/21`
`b)`
`-5/12+(x-2)/-4=1/3`
`=>(x-2)/(-4)=1/3+5/12`
`=>(x-2)/-4=4/12+5/12`
`=>(x-2)/-4=9/12`
`=>(x-2)/-4=3/4`
`=>(-(x-2))/4=3/4`
`=>-(x-2)=3`
`=>-x+2=3`
`=>-x=3-2`
`=>-x=1`
`=>x=-1`
Vậy `x=-1`
`c)`
`5/(x-1)+4/(x-1)=-3/7(x\ne1)`
`=>(5+4)/(x-1)=-3/7`
`=>9/(x-1)=-3/7`
`=>(x-1).(-3)=9.7`
`=>-3x+3=63`
`=>-3x=63-3`
`=>-3x=60`
`=>x=60:(-3)`
`=>x=-20`
Vậy `x=-20`