Đáp án + Giải thích các bước giải:
`a//`
`A=((x^{2}-3)/(x^{2}-9)+(1)/(x-3)):(x)/(x+3)`
`=((x^{2}-3)/((x-3)(x+3))+(x+3)/((x-3)(x+3))).(x+3)/(x)`
`=((x^{2}-3+x+3)/((x-3)(x+3))).(x+3)/(x)`
`=(x^{2}+x)/((x-3)(x+3)).(x+3)/(x)`
`=((x^{2}+x)(x+3))/(x(x-3)(x+3))`
`=(x(x+1)(x+3))/(x(x-3)(x+3))`
`=(x+1)/(x-3)`
`b//`
`|A|=3`
`->A=±3`
`+` TH1 :
`A=3`
`<=>(x+1)/(x-3)=3`
`<=>3(x-3)=x+1`
`<=>3x-9=x+1`
`<=>3x-x=9+1`
`<=>2x=10`
`<=>x=5 (TM)`
`+` TH2:
`A=-3`
`<=>(x+1)/(x-3)=-3`
`<=>-3(x-3)=x+1`
`<=>-3x+9=x+1`
`<=>x+3x=9-1`
`<=>4x=8`
`<=>x=2 (TM)`