Cho hàm số
có đạo hàm
Số điểm cực trị của hàm số
là:
A.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020022894076986889413/image2020022894076986889413632530_images/image2020022894076986889413632530_img1.png)
B.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020022894076986889413/image2020022894076986889413555014_images/image2020022894076986889413555014_img1.png)
C.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020022894076986889413/image2020022894076986889413158561_images/image2020022894076986889413158561_img1.png)
D.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020022894076986889413/image2020022894076986889413505556_images/image2020022894076986889413505556_img1.png)
Đáp án và lời giải
Đáp án:C
Lời giải:Lời giải
Ta có
.
Ta có bảng biến thiên:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020022894076986889413/image2020022894076986889413378582_images/image2020022894076986889413378582_img1.png)
Vậy hàm số
có 2 điểm cực trị.
Ta có
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020022894076986889413/image2020022894076986889413428040_images/image2020022894076986889413428040_img1.png)
Ta có bảng biến thiên:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020022894076986889413/image2020022894076986889413378582_images/image2020022894076986889413378582_img1.png)
Vậy hàm số
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2020022894076986889413/image2020022894076986889413267139_images/image2020022894076986889413267139_img1.png)