[tex]\displaystyle\bf\\f(x)=x^{2} -3x+2\\\\f(x)=0\\\\x^{2} -3x+2=0\\\\Teorema \ Vieta \ :\\\\x_{1} + x_{2} =3\\\\x_{1} \cdot x_{2} =2\\\\\boxed{x_{1} =1 \ \ \ , \ \ \ x_{2} =2}[/tex]

При x = 1  и  x = 2  значение функции равно нулю .