①x2-2x-2=0
x²-2x+1=3;
(x-1)²=3;
x-1=±√3;
x=1±√3;
②x2+8x-9=0
x²+8x+16=25;
(x+4)²=25;
x+4=±5;
x=-4±5;
x=-9或1
③2x2+1=-3x
2x²+3x=-1;
2(x+3/4)²=-1+9/8;
2(x+3/4)²=1/8;
(x+3/4)²=1/16;
x+3/4=±1/4;
x=-3/4±1/4;
x=-1或x=-1/2；
④3x2-6x+4=0
3(x-1)²+1=0;
無(wú)解