<img src="https://storage.tutusouti.com/pzst/question_bank/res/15/87/15876cf18ccc94cfc5f6002c38a74d09aa08f2e9.jpg?x-oss-process=image/sharpen,200"/>，当<img src="https://storage.tutusouti.com/pzst/question_bank/res/23/4f/234f9e9014540d781c0e18c9ae6e201c43513f4f.jpg?x-oss-process=image/sharpen,200"/>满足条件（）时收敛