当x=2,y=1/2时,求代数式(x+y)(x-y)+(x-y)2-(x2-3xy)的值.
问题描述:
当x=2,y=
时,求代数式(x+y)(x-y)+(x-y)2-(x2-3xy)的值. 1 2
答
(x+y)(x-y)+(x-y)2-(x2-3xy),
=x2-y2+x2-2xy+y2-x2+3xy,
=x2+xy,
当x=2,y=
时,原式=22+2×1 2
=5.1 2