问题 填空题
已知函数f(x)=
1
4x+2
(x∈
R),若x1+x2=1,则f(x1)+f(x2)=______;若n∈N*,则f(
1
n
)+f(
2
n
)+…+f(
n-1
n
)+f(
n
n
)
=______.
答案

∵函数f(x)=

1
4x+2
(x∈R),

∴f(x1)=

1
4x1+2

又∵x1+x2=1,x2=1-x1

∴f(x2)=

1
4(1-x1)+2

f(x1)+f(x2)=

1
4x1+2
+
1
4(1-x1)+2
=
2
2•4x1+4
+
4x1
4 +2•4x1
=
2+4x1
4 +2•4x1
=
1
2

f(

1
n
)+f(
2
n
)+…+f(
n-1
n
)+f(
n
n
)

=[f(

1
n
)+f(
n-1
n
)]+[f(
2
n
)+f(
n-1
n
)]+…+f(
n
n
)

=

n-1
2
1
2
+f(1)

=

n
4
-
1
12

故答案为:

1
2
n
4
-
1
12

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