>
数学
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已知x+y=2,则
1
2
x
2
+xy+
1
2
y
2
等于( )
A. 2
B. 4
C.
1
2
D. -2
人气:198 ℃ 时间:2019-11-18 05:02:30
解答
∵x+y=2,
∴
1
2
x
2
+xy+
1
2
y
2
=
1
2
(x
2
+2xy+y
2
)=
1
2
(x+y)
2
=
1
2
×2
2
=2.
故选A.
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