Tính tổng
ta được kết quả là:
A.
.
![img1](https://cungthi.online/upload/questionbank3/eduquestion/2019331968172115733/obj2019331968172115733833099_images/obj2019331968172115733833099_img1.png)
B.
.
![img1](https://cungthi.online/upload/questionbank3/eduquestion/2019331968172115733/obj2019331968172115733483169_images/obj2019331968172115733483169_img1.png)
C.
.
![img1](https://cungthi.online/upload/questionbank3/eduquestion/2019331968172115733/obj2019331968172115733133240_images/obj2019331968172115733133240_img1.png)
D.
.
![img1](https://cungthi.online/upload/questionbank3/eduquestion/2019331968172115733/obj2019331968172115733353260_images/obj2019331968172115733353260_img1.png)
Đáp án và lời giải
Đáp án:C
Lời giải:Phân tích:
Ta có : ![img1](https://cungthi.online/upload/questionbank3/eduquestion/2019331968172115733/obj2019331968172115733910684_images/obj2019331968172115733910684_img1.png)
.
Cho
ta được:
.
Vậy đáp án đúng là C.
![img1](https://cungthi.online/upload/questionbank3/eduquestion/2019331968172115733/obj2019331968172115733910684_images/obj2019331968172115733910684_img1.png)
![img2](https://cungthi.online/upload/questionbank3/eduquestion/2019331968172115733/obj2019331968172115733910684_images/obj2019331968172115733910684_img2.png)
![img3](https://cungthi.online/upload/questionbank3/eduquestion/2019331968172115733/obj2019331968172115733910684_images/obj2019331968172115733910684_img3.png)
![img4](https://cungthi.online/upload/questionbank3/eduquestion/2019331968172115733/obj2019331968172115733910684_images/obj2019331968172115733910684_img4.png)
![img5](https://cungthi.online/upload/questionbank3/eduquestion/2019331968172115733/obj2019331968172115733910684_images/obj2019331968172115733910684_img5.png)