问题 填空题
已知整数x、y满足:1<x<y<100,且x
y
+y
x
-
2009x
-
2009y
+
2009xy
=2009

则:
x+y+10
=______.
答案

x

y
+y
x
-
2009x
-
2009y
+
2009xy
=2009

xy
x
+
y
)-
2009
x
+
y
)+
2009xy
-
20092
=0

x
+
y
+
2009
)(
xy
-
2009
)=0

∵1<x<y<100

xy
-
2009
=0

∴xy=2009=7×7×41=49×41

∵整数x、y满足:1<x<y<100

∴x=41,y=49

x+y+10
=
41+49+10
=
100
=10.

故本题答案为:10.

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