Cho hàm số
xác định và có đạo hàm trên
thỏa mãn
. Viết phương trình tiếp tuyến của đồ thị hàm số
tại điểm có hoành độ bằng
.
A.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034968103_images/obj2019301968158593034968103_img1.png)
B.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034937110_images/obj2019301968158593034937110_img1.png)
C.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034760678_images/obj2019301968158593034760678_img1.png)
D.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034729685_images/obj2019301968158593034729685_img1.png)
Đáp án và lời giải
Đáp án:B
Lời giải:Phân tích:
Từ
(*), cho
ta có ![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img3.png)
Đạo hàm hai vế của (*) ta được
.
Cho
ta được ![img7](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img7.png)
(**).
Nếu
thì (**) vô lý, do đó
, khi đó (**) trở thành
![img11](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img11.png)
Phương trình tiếp tuyến
.
Vậy đáp án đúng là B.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img2.png)
![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img3.png)
![img4](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img4.png)
![img5](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img5.png)
![img6](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img6.png)
![img7](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img7.png)
![img8](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img8.png)
![img9](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img9.png)
![img10](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img10.png)
![img11](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img11.png)
![img12](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img12.png)
![img13](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img13.png)
![img14](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019301968158593034/obj2019301968158593034426279_images/obj2019301968158593034426279_img14.png)