b) [tex]\sqrt{3x-1}=a[/tex]
[tex]\sqrt{x+1}=b[/tex]
[tex]a^3-a=a^2b-b-b^2+ab<=>a^2(a-b)=a-b+b(a-b)<=>(a-b)(a^2-1-b)=0=> a=b \vee a^2-1-b=0[/tex]
[tex]\sqrt{3x-1}=\sqrt{x+1}[/tex] tự giải nha
[tex]a^2-1-b=0<=>3x-1-1-\sqrt{x+1}=0<=>3x-2=\sqrt{x+1}[/tex] ( tự giải nha )