题目内容
设x＞0,y＞0,且xy-(x+y)=1,则( )A.x+y≥2(
+1) B.xy≤
+1
C.xy≥(
+1)2 D.xy≥2(
+1)
答案：C
解析:∵x＞0,y＞0,∴x+y≥2.
∴-(x+y)≤-2,xy-(x+y)≤xy-2,即xy-2-1≥0.
设t=
(t＞0),则t2-2t-1≥0.
解得t≥
+1,即
≥
+1.
所以xy≥(
+1)2.
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题目内容
设x＞0,y＞0,且xy-(x+y)=1,则( )A.x+y≥2(+1) B.xy≤+1
C.xy≥(+1)2 D.xy≥2(+1)
答案：C
解析:∵x＞0,y＞0,∴x+y≥2.
∴-(x+y)≤-2,xy-(x+y)≤xy-2,即xy-2-1≥0.
设t=(t＞0),则t2-2t-1≥0.
解得t≥+1,即≥+1.
所以xy≥(+1)2.
=1,则x
的最大值是________________________.
,b=
,c=
(
),d=
,则a,b,c,d中最小的是( )
B.
≥1
≥2 D.
≥9.