Đáp án:
`a,5-(x-6)=2(9-4x)`
`<=>5-x+6=18-8x`
`<=>7x=7`
`<=>x=1`
`b,(3x-11)/12=(3x-5)/4-(2x-3)/9`
`<=>(3(3x-11))/36=(9(3x-5)-4(2x-3))/(36)`
`=>9x-33=27x-45-8x+12`
`<=>-10x=0`
`<=>x=0`
`c,(x-1)/(x+2)-x/(x-2)=(3x-5)/(4-x^2) (đk: x\ne+-2)`
`<=>((x-1)(x-2)-x(x+2))/(x^2-4)=(-3x+5)/(x^2-4)`
`=>-5x+2=-3x+5`
`<=>x=-3/2(\text{tmđk})`
