(1)Rn=1.1*R_(n-1)-0.15*F_(n-1)
Fn=0.85*F_(n-1)+0.1R_(n-1)
于是
Rn-Fn=R_(n-1)-F_(n-1)
因此{Rn-Fn}为常数列
所以Rn-Fn=R0-F0=70,Rn=Fn+70
(2)由(1)得
Rn=1.1*R_(n-1)-0.15[R_(n-1)-70]
=0.95R_(n-1)+10.5
两边都减210得
Rn-210=0.95*[R_(n-1)-210]
故{Rn-210}是以-110为第0项,0.95为公比的等比数列
所以Rn-210=-110*(0.95)^n
Rn=210-110*(0.95)^n
同理,由
Fn=0.95F_(n-1)+7得
Fn-140=0.95[F_(n-1)-140]
Fn=140-40*(0.95)^n
(3)n→∞时
Rn→210,Fn→140,故能平衡