\(a) 2x^3-x^2-2x+1=0\\↔x^2(2x-1)-(2x-1)=0\\↔(x^2-1)(2x-1)=0\\↔(x-1)(x+1)(2x-1)=0\\↔x-1=0\quad or\quad x+1=0\quad or\quad 2x-1=0\\↔x=1\quad or\quad x=-1\quad or\quad x=\dfrac{1}{2}\\\text{Vậy pt có tập nghiệm}\,\,S=\{1;-1;\dfrac{1}{2}\}\\b) 2x^2-x=3-6x\\↔2x^2-x+6x-3=0\\↔(2x^2+6x)-(x+3)=0\\↔2x(x+3)-(x+3)=0\\↔(2x-1)(x+3)=0\\↔2x-1=0\quad or\quad x+3=0\\↔x=\dfrac{1}{2}\quad or\quad x=-3\\\text{Vậy pt có tập nghiệm}\,\,S=\{\dfrac{1}{2};-3\}\\c)\dfrac{y^2-6}{y}=3y+1(y\ne 0)\\↔y^2-6=y(3y+1)\\↔y^2-6=3y^2-y\\↔y^2-3y^2-y-6=0\\↔-2y^2-y-6=0\\↔y^2+\dfrac{1}{2}y+3=0\\↔y^2+2.\dfrac{1}{4}.y+\dfrac{1}{16}+\dfrac{47}{16}=0\\↔(y+\dfrac{1}{4})^2+\dfrac{47}{16}=0(vô\,\,lý)\\\text{Vậy pt vô nghiệm}\,\,S=\varnothing\)
