x²-4x+1=0,x²-4x+4=3(x-2)^2=3x-2=根号3 x-2=-根号3x=2+根号3 x=2-根号3x²+3x+1=0x^2+3x+9/4=5/41/4 (3 + 2 x)^2=5/43+2x=根号5 3+2x=-根号5x=(根号5-3)/2 x=-(3+根号5)/2