因式分解 x^2n+6x^n-y^2+9
问题描述：
因式分解 x^2n+6x^n-y^2+9
答
原式=（x^n+3)^2-y^2=(x^2+3-y)(x^2+3+y).
答
原式＝(x^n)^2+6x^n+9-y^2
=(x^n+3)^2-y^2
=(x^n+3+y)(x^n+3-y)