x^2-6x+c=0
(3-\sqrt2)^2-6(3-\sqrt2)+c=0
9-2*3*\sqrt2+2-18+6\sqrt2+c=0
9-6\sqrt2-16+6\sqrt2+c=0
c-7=0
c=7
x^2-6x+7=0
\Delta=b^2-4ac=36-4*1*7=36-28=8
\sqrt\Delta=\sqrt8=\sqrt{4*2}=2\sqrt2
x_1=\frac{-b-\sqrt\Delta}{2a}=\frac{6-2\sqrt2}{2}=3-\sqrt2
x_2=\frac{-b+\sqrt\Delta}{2a}=\frac{6+2\sqrt2}{2}=3+\sqrt2 <-- odpowiedź