已知:xy=-1,求代数式(x=2y)²-(x-2y)²的值
问题描述:
已知:xy=-1,求代数式(x=2y)²-(x-2y)²的值
答
(x+2y)²-(x-2y)²
=x²+4xy+4y²-x²+4xy-4y²
=8xy
=-8