你题目是不是：x^2-y^2-6x+9= (x^2-6x+9)-y^2=(x-3)^2-y^2=(x-3+y)(x-3-y)=(x+y-3)(x-y-3)如是计算则应是下面,你看看吧x^2-y^2-6x=9x^2+6x+9+y^2=0(x+3)^2+y^2=0且 (x+3)^2≥0,y^2≥0所以：(x+3)^2=0 y^2=0x+3=0 y=0...