2(x-3)=x²-9
(x²-9)-2(x-3)=0
(x-3)(x+3)-2(x-3)=0
(x-3)[(x+3)-2]=0
(x-3)(x+1)=0
x-3=0 或 x+1=0
x1=3
x2=-1
用分解因式法解方程：2(x-3)=x2-9.一定要分解因式法!
2(x-3)=x²-9
(x²-9)-2(x-3)=0
(x-3)(x+3)-2(x-3)=0
(x-3)[(x+3)-2]=0
(x-3)(x+1)=0
x-3=0 或 x+1=0
x1=3
x2=-1