Hệ thức truy hồi nào dưới đây cũng là một công thức xác định dãy số
cho bởi công thức
.
A.
với
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020160268845697490/obj2020160268845697490319433_images/obj2020160268845697490319433_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020160268845697490/obj2020160268845697490319433_images/obj2020160268845697490319433_img2.png)
B.
với
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020160268845697490/obj2020160268845697490260314_images/obj2020160268845697490260314_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020160268845697490/obj2020160268845697490260314_images/obj2020160268845697490260314_img2.png)
C.
với
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020160268845697490/obj2020160268845697490278711_images/obj2020160268845697490278711_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020160268845697490/obj2020160268845697490278711_images/obj2020160268845697490278711_img2.png)
D.
với
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020160268845697490/obj2020160268845697490963039_images/obj2020160268845697490963039_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020160268845697490/obj2020160268845697490963039_images/obj2020160268845697490963039_img2.png)
Đáp án và lời giải
Đáp án:B
Lời giải:
Ta có:
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020160268845697490/obj2020160268845697490175934_images/obj2020160268845697490175934_img1.png)