Có bao nhiêu số phức thỏa mãn
?
A. 2.
B. 3.
C.1.
D. 4.
Đáp án và lời giải
Đáp án:B
Lời giải:Phân tích:
Đặt
, khi đó ta có
Xét hàm số
, có bảng biến thiên là
Đường thẳng
cắt đồ thị hàm số
tại hai điểm nên phương trình
có hai nghiệm khác 1 (do
). Thay giá trị môđun của z vào kiểm tra đều được kết quả đúng.
Vậy có 3 số phức thỏa mãn điều kiện.
![img1](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img1.png)
![img2](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img2.png)
![img3](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img3.png)
![img4](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img4.png)
![img5](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img5.png)
![img6](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img6.png)
![img7](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img7.png)
![img8](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img8.png)
![img9](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img9.png)
![img10](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img10.png)
![img11](https://cungthi.online/upload/questionbank3/eduquestion/20183401557915949495/obj20183401557915949495877215_images/obj20183401557915949495877215_img11.png)