已知x=2-3,y=2+3,求下列代数式的值: (1)x2+2xy+y2; (2)x2-y2.
问题描述:
已知x=2-
,y=2+
3
,求下列代数式的值:
3
(1)x2+2xy+y2;
(2)x2-y2.
答
(1)∵x=2-
,y=2+
3
,
3
∴x+y=4,
∴x2+2xy+y2=(x+y)2=42=16;
(2))∵x=2-
,y=2+
3
,
3
∴x+y=4,x-y=-2
,
3
∴x2-y2=(x+y)(x-y)
=4×(-2
)
3
=-8
.
3