x2-2x-1=0即x2-2x+1=2即(x-1)2=2即x-1=±√(2)即x=√(2)-1或x=-√(2)-1
x²-2x-1=0（x-1)²-2=0(x-1)²=2x-1=±√2x=1+√2或x=1-√2
