解：x²+2x-15=0 =>x²+2x=15上式两边同加1得：(x+1)²=4²x+1=±4x1=-5 x2=3
x^2+2x-15=0(x+5)(x-3)=0x=-5 或 x=3
(x+5)(x-3)=0x=-5,x=3
