Đáp án+Giải thích các bước giải:
`a)x-(x+1)/3=2x+1/5`
`<=>(15x)/15-(5(x+1))/15=(3(2x+1))/15`
`<=>15x-5(x+1)=3(2x+1)`
`<=>15x-5x-5=6x+3`
`<=>10x-5=6x+3`
`<=>10x-6x=3+5`
`<=>4x=8`
`<=>x=2`
Vậy `S=\{2\}`
`b)ĐKXĐ:x\ne 0;x\ne -1`
`(x-1)/x+1/(x+1)=(2x+1)/(x^2+x)`
`<=>((x-1)(x+1))/(x(x+1))+(1.x)/(x(x+1))=(2x+1)/(x(x+1))`
`=>(x-1)(x+1)+x=2x+1`
`<=>x^2-1+x=2x+1`
`<=>x^2-1+x-2x-1=0`
`<=>x^2-x-2=0`
`<=>x^2-2x+x-2=0`
`<=>x(x-2)+(x-2)=0`
`<=>(x-2)(x+1)=0`
`<=>x-2=0` $\text{hoặc}$ `x+1=0`
`<=>x=2(TM)` $\text{hoặc}$ `x=-1(KTM)`
Vậy `S=\{2\}`
