Ta có: [tex]x^2-3x+2=(x-1)(x-2)\Rightarrow \left\{\begin{matrix} f(x)\vdots x-1\\ f(x)\vdots x-2 \end{matrix}\right.\Rightarrow \left\{\begin{matrix} f(2)=0\\ f(1)=0 \end{matrix}\right.\Rightarrow \left\{\begin{matrix} 4a+2b=-15\\ a+b=0 \end{matrix}\right.\Rightarrow a=-7,5,b=7,5[/tex]