Gọi
,
là các số thực dương thỏa mãn điều kiện
và
, với
,
là hai số nguyên dương. Tính
.
![img1](https://cungthi.online/upload/questionbank3/eduquestion/2019403175456418519/obj2019403175456418519949618_images/obj2019403175456418519949618_img1.png)
![img2](https://cungthi.online/upload/questionbank3/eduquestion/2019403175456418519/obj2019403175456418519949618_images/obj2019403175456418519949618_img2.png)
![img3](https://cungthi.online/upload/questionbank3/eduquestion/2019403175456418519/obj2019403175456418519949618_images/obj2019403175456418519949618_img3.png)
![img4](https://cungthi.online/upload/questionbank3/eduquestion/2019403175456418519/obj2019403175456418519949618_images/obj2019403175456418519949618_img4.png)
![img5](https://cungthi.online/upload/questionbank3/eduquestion/2019403175456418519/obj2019403175456418519949618_images/obj2019403175456418519949618_img5.png)
![img6](https://cungthi.online/upload/questionbank3/eduquestion/2019403175456418519/obj2019403175456418519949618_images/obj2019403175456418519949618_img6.png)
![img7](https://cungthi.online/upload/questionbank3/eduquestion/2019403175456418519/obj2019403175456418519949618_images/obj2019403175456418519949618_img7.png)
A.
B.
C.
D.
Đáp án và lời giải
Đáp án:D
Lời giải:
Phân tích: Đặt . Suy ra
.
. Mặt khác
suy ra
. Vậy
.
Vậy đáp án đúng là D.