1、x²-2√5x+2=0
x²－2√5x＋5＝3
﹙x－√5﹚²＝3
x－√5=±√3
x1=√5＋√3,x2=√5－√3
2、(2Y+1)^2+3(2Y+1)+2=0
[(2y+1)+2][(2y+1)+1]=0
(2y+3)(2y+2)=0
2y+3=0,2y+2=0
y1=-3/2,y2=-1
3、x²-(1+2√3）x+3+√3=0,
x^2-(1+2√3)x+√3(√3+1)=0,
(x-√3)(x-√3-1)=0,
x1=√3,x2=√3+1
4、(x²-2)²-3(x²-2)=0
（x²-2）（x²-2-3）=0
x1=+√2,x2=-√2,x3=+√5,x4=-√5