Tìm giá trị đúng của
.
A.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20205306524368563393/obj20205306524368563393446080_images/obj20205306524368563393446080_img1.png)
B.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20205306524368563393/obj20205306524368563393886191_images/obj20205306524368563393886191_img1.png)
C.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20205306524368563393/obj20205306524368563393170870_images/obj20205306524368563393170870_img1.png)
D.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20205306524368563393/obj20205306524368563393514999_images/obj20205306524368563393514999_img1.png)
Đáp án và lời giải
Đáp án:C
Lời giải:
Ta có:
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20205306524368563393/obj20205306524368563393571253_images/obj20205306524368563393571253_img1.png)