các bạn giải giúp mik vs ạ

Đáp án:

`a)`

`2.(4x-7)=3.(x+1)+18`

`<=>8x-14=3x+3+18`

`<=>8x-3x-14=21`

`<=>5x=21+14`

`<=>5x=35`

`<=>x=7`

Vậy `S={7}`

`b)`

`\frac{-2x-4}{5}=\frac{2x-1}{-3}-2`

`<=>\frac{-2x-4}{5}=\frac{1-2x}{3}-2`

`<=>\frac{3.(-2x-4)}{15}=\frac{5.(1-2x)}{15}-\frac{15.2}{15}`

`<=>3.(-2x-4)=5.(1-2x)-30`

`<=>-6x-12=5-10x-30`

`<=>-6x+10x=-25+12`

`<=>4x=-13`

`<=>x=-13/4`

Vậy `S={-13/4}`

`c)`

`(2x-4).(2x-1)=(2x-3)^{2}`

`<=>4x^{2}-2x-8x+4=(2x)^{2}-2.2x.3+3^{2}`

`<=>4x^{2}-10x+4=4x^{2}-12x+9`

`<=>4x^{2}-10x+4-4x^{2}+12x-9=0`

`<=>2x-5=0`

`<=>2x=5`

`<=>x=5/2`

Vậy `S={5/2}`

`d)`

`(3x+1).(2/5x-1)=0`

`<=>3x+1=0` hoặc `2/5x-1=0`

`<=>3x=-1` hoặc `2/5x=1`

`<=>x=-1/3` hoặc `x=1: 2/5`

`<=>x=-1/3` hoặc `x=5/2`

Vậy `S={-1/3;5/2}`

`e)`

`x^{2}-4+(x-9).(x-2)=0`

`<=>(x+2).(x-2)+(x-9).(x-2)=0`

`<=>(x-2).(x+2+x-9)=0`

`<=>(x-2).(2x-7)=0`

`<=>x-2=0` hoặc `2x-7=0`

`<=>x=2` hoặc `2x=7`

`<=>x=2` hoặc `x=7/2`

Vậy `S={2;7/2}`

`f)`

`\frac{x+2}{x+3}+\frac{2x-1}{x-3}=\frac{13x-9}{x^{2}-9}` `(đk: x\ne\pm3)`

`<=>\frac{(x+2).(x-3)}{(x+3).(x-3)}+\frac{(2x-1).(x+3)}{(x+3).(x-3)}=\frac{13x-9}{(x+3).(x-3)}`

`=>(x+2).(x-3)+(2x-1).(x+3)=13x-9`

`<=>x^{2}-3x+2x-6+2x^{2}+6x-x-3=13x-9`

`<=>3x^{2}+4x-9-13x+9=0`

`<=>3x^{2}-9x=0`

`<=>3x.(x-3)=0`

`<=>3x=0` hoặc `x-3=0`

`<=>x=0(tmđk)` hoặc `x=3(ktmđk)`

`=>x=0`

Vậy `S={0}`