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=

1
2
时,求代数式(x+y)(x-y)+(x-y)2-(x2-3xy)的值.

(x+y)(x-y)+(x-y)2-(x2-3xy),
=x2-y2+x2-2xy+y2-x2+3xy,
=x2+xy,
当x=2,y=

1
2
时,原式=22+2×
1
2
=5.