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
,Q=b b+1
+1 a+1
,则P______Q(填“>”、“<”或“=”). 1 b+1
答
∵P=
=a(b+1)+b(a+1) (a+1)(b+1)
,把ab=1代入得:2ab+a+b ab+a+b+1
=1;2+a+b 2+a+b
Q=
=b+1+a+1 (a+1)(b+1)
,把ab=1代入得:a+b+2 ab+a+b+1
=1;2+a+b 2+a+b
∴P=Q.