Cho
,
. Tính
theo
và
:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20185307579718513868/obj20185307579718513868340371_images/obj20185307579718513868340371_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20185307579718513868/obj20185307579718513868340371_images/obj20185307579718513868340371_img2.png)
![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20185307579718513868/obj20185307579718513868340371_images/obj20185307579718513868340371_img3.png)
![img4](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20185307579718513868/obj20185307579718513868340371_images/obj20185307579718513868340371_img4.png)
![img5](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20185307579718513868/obj20185307579718513868340371_images/obj20185307579718513868340371_img5.png)
A.
B.
C.
D.
Đáp án và lời giải
Đáp án:A
Lời giải:
Phân tích: Ta xét . Do đó
.
Đáp án đúng là A