我又来问题了.........

分子用平方差，可化为：(x^2+y^2-9+2xy)(x^2+y^2-9-2xy)再用平方差公式后最可化为：(x+y+3)(x+y-3)(x-y+3)(x-y-3)。分母则可化为：(x+3)^2-y^2最后化为：(x+y+3)(x-y+3)。约分后得：(x+y-3)(x-y-3)

(x^2+y^2-9)^2-4x^2y^2 / x^2-y^2+6x+9
=(x^2+y^2-9+2xy)(x^2+y^2-9-2xy)/(x+3)^2-y^2
=[(x+y)^2-9][(x-y)^2-9]/(x+3+y)(x+3-y)
=(x+y+3)(x+y-3)(x-y+3)(x-y-3)/(x+y+3)(x-y+3)
=(x+y-3)(x-y-3)
=(x-3)^2-y^2
=x^2-6x+9-y^2
=x^2-y^2-6x+9

写清楚先！谢谢~~~

我怎么看不懂啊?

x^2是什么意思?解释一下