x²+2x-1=0x²+x2=1x²+x2+1-1=1(x+1)²-1=1(x+1)²=2x+1=正负根号2x1=根号2-1x²=负根号2-1
x²+2x-1=0x²+2x+1-2=0(x+1)^2-2=0(x+1+√2）（x+1-√2）=0x1=-1+√2x2=-1-√2
x²+2x-1=0x²+2x+1=2x+1=±√2x=-1±√2x1=-1+√2x2=-1-√2
