已知y-2x=0,求代数式(x²-y²)(x²-xy+y²)/(x²+xy+y²)(x²-y²)的值

问题描述:

已知y-2x=0,求代数式(x²-y²)(x²-xy+y²)/(x²+xy+y²)(x²-y²)的值

即y=2x
所以原式=(x²-xy+y²)/(x²+xy+y²)
=(x²-2x²+4x²)/(x²+2x²+4x²)
=3x²/7x²
=3/7