1,若x不等于0是x^2+xy+y^2=0,则(x^2+3xy+y^2)/(x^2+y^2)=?
问题描述：
1,若x不等于0是x^2+xy+y^2=0,则(x^2+3xy+y^2)/(x^2+y^2)=?
2.因式分解：4x^4-13x^2+9
3.因式分解：（x^2-2x）^2-7(x^2-2z)+12
答
1,
x^2+xy+y^2=0 则
x^2+3xy+y^2
=（x^2+xy+y^2）+2xy
=0+2xy
=2xy
x^2+y^2
=（x^2+xy+y^2）-xy
=0-xy
=-xy
则
(x^2+3xy+y^2)/(x^2+y^2)
=2xy/-xy
=-2
-----------------------------
2,
4x^4-13x^2+9
=(x^2-1)(4x^2-9)
=(x-1)(x+1)(2x-3)(2x+3)
--------------------------
3,(楼主:z应改成x)
（x^2-2x）^2-7(x^2-2x)+12
=(x^2-2x-4)(x^2-2x-3)
=(x^2-2x-4)(x-3)(x+1)