(x-5y)(-x-5y)-(-x+5y)^2,其中x=0.5,y=-1.计算
问题描述：
(x-5y)(-x-5y)-(-x+5y)^2,其中x=0.5,y=-1.计算
答
(x-5y)(-x-5y)-(-x+5y)^2
=(-5y+x)(-5y-x)-(x^2-10xy+25y^2
=25y^2-x^2-x^2+10xy-25y^2
=10xy-2x^2
=10*0.5*(-1)-2*0.5^2
=-5-0.5
=-5.5