a、b为实数,且ab=1,设P=a/a+1+b/b+1,Q=1/a+1+1/b+1,则P_Q(填“>”、“<”或“=”).

问题描述:

a、b为实数,且ab=1,设P=

a
a+1
+
b
b+1
,Q=
1
a+1
+
1
b+1
,则P______Q(填“>”、“<”或“=”).

∵P=

a(b+1)+b(a+1)
(a+1)(b+1)
=
2ab+a+b
ab+a+b+1
,把ab=1代入得:
2+a+b
2+a+b
=1;
Q=
b+1+a+1
(a+1)(b+1)
=
a+b+2
ab+a+b+1
,把ab=1代入得:
2+a+b
2+a+b
=1;
∴P=Q.