[Mức độ 4] Cho hàm số
. Hàm số
có đồ thị như hình bên.
Hàm số
đồng biến trên khoảng nào dưới đây?
A.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756821263_images/obj202024031084549362756821263_img1.png)
B.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756787336_images/obj202024031084549362756787336_img1.png)
C.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756898848_images/obj202024031084549362756898848_img1.png)
D.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756545984_images/obj202024031084549362756545984_img1.png)
Đáp án và lời giải
Đáp án:A
Lời giải:
Ta có: ![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img1.png)
.
Đặt
.
Vẽ đường thẳng
và đồ thị hàm số
trên cùng một hệ trục.
Hàm số
đồng biến biến
Như vậy
.
Vậy hàm số
đồng biến trên các khoảng
và
.
Mà
nên hàm số
đồng biến trên khoảng
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img2.png)
![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img3.png)
![img4](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img4.png)
![img5](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img5.png)
![img6](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img6.png)
![img7](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img7.png)
![img8](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img8.png)
![img9](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img9.png)
![img10](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img10.png)
![img11](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img11.png)
![img12](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img12.png)
![img13](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img13.png)
![img14](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img14.png)
![img15](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img15.png)
![img16](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202024031084549362756/obj202024031084549362756577045_images/obj202024031084549362756577045_img16.png)