Trong không gian với hệ tọa độ Oxyz cho điểm
và đường thẳng
. Viết phương trình mặt phẳng (P) chứa
sao cho khoảng cách từ A tới (P) là lớn nhất:
A.A:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463130387_images/obj20174712102610780463130387_img1.png)
B.B:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463223434_images/obj20174712102610780463223434_img1.png)
C.C:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463461921_images/obj20174712102610780463461921_img1.png)
D.D:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463554967_images/obj20174712102610780463554967_img1.png)
Đáp án và lời giải
Đáp án:C
Lời giải:Đáp án C
Gọi
là hình chiếu vuông góc của A trên
.
Khi đó:
.
Cho
Ta có:
, dấu bằng xảy ra
Mặt khác:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463617022_images/obj20174712102610780463617022_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463617022_images/obj20174712102610780463617022_img2.png)
![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463617022_images/obj20174712102610780463617022_img3.png)
![img4](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463617022_images/obj20174712102610780463617022_img4.png)
![img5](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463617022_images/obj20174712102610780463617022_img5.png)
![img6](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463617022_images/obj20174712102610780463617022_img6.png)
![img7](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20174712102610780463/obj20174712102610780463617022_images/obj20174712102610780463617022_img7.png)