先化简,再求值(3x-5y)^2-(3x+5y)^2,其中x=2008,y=-1/2008
问题描述:
先化简,再求值(3x-5y)^2-(3x+5y)^2,其中x=2008,y=-1/2008
答
(3x-5y)^2-(3x+5y)^2
=(3x)^2-30xy+(5y)^2-(3x)^2-30xy-(5y)^2
=-60xy
=-60×2008×(-1/2008)
=60