答：
2(x-3)²=x²-9
2(x-3)²-(x²-3²)=0
2(x-3)²-(x-3)(x+3)=0
(x-3)*[2(x-3)-(x+3) ]=0
(x-3)(2x-6-x-3)=0
(x-3)(x-9)=0
解得：x1=3,x2=9