已知0＜X1＜3,Xn=根号下Xn-1(3-Xn-1）证明｛Xn｝极限存在,并求极限

题目

已知0＜X1＜3,Xn=根号下Xn-1(3-Xn-1）证明｛Xn｝极限存在,并求极限

答案

证明：因为0<x1<3所以x(n+1)<=[xn+(3-xn)]/2=3/2所以｛xn}有界又x(n+1)=√[Xn(3-Xn)]>=√[Xn(3-3/2)]=√(3/2)xn>=xn所以{xn}递增单调有界数列必有极限,设x=limxn=limx(n+1),则x=√x(3-x)解得x=3...