[Mức độ 2] Cho hàm số bậc ba
có đồ thị như hình vẽ. Mệnh đề nào dưới đây đúng?
A.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895734465_images/obj202048021084327594895734465_img1.png)
B.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895700537_images/obj202048021084327594895700537_img1.png)
C.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895242099_images/obj202048021084327594895242099_img1.png)
D.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895208172_images/obj202048021084327594895208172_img1.png)
Đáp án và lời giải
Đáp án:C
Lời giải:
Đồ thị hàm số
.
Do
.
Đồ thị cắt trục
tại điểm có tung độ âm nên
.
Hàm số đạt cực trị tại hai điểm phân biệt có hoành độ dương nên
có hai nghiệm dương phân biệt
Suy ra:
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895663744_images/obj202048021084327594895663744_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895663744_images/obj202048021084327594895663744_img2.png)
![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895663744_images/obj202048021084327594895663744_img3.png)
![img4](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895663744_images/obj202048021084327594895663744_img4.png)
![img5](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895663744_images/obj202048021084327594895663744_img5.png)
![img6](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895663744_images/obj202048021084327594895663744_img6.png)
![img7](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202048021084327594895/obj202048021084327594895663744_images/obj202048021084327594895663744_img7.png)