Question

圆x^2+y^2-2x-1=0关于直线2x-y+3=0对称的圆的方程是（ ）

圆x^2+y^2-2x-1=0关于直线2x-y+3=0对称的圆的方程是（ ）
A.(x+3)^2+(y-2)^2=1/2
B.(x-3)^2+(y+2)^2=1/2
C.(x+3)^2+(y-2)^2=2
D.(x-3)^2+(y+2)^2=2

要详细过程，网上的我有些看不大懂额

Answer 1

x^2+y^2-2x-1=0的变形是y^2+(x-1）^2=2，所以这个圆的圆心是（1,0），半径是必须在中线根号2，对称的圆至少要和原来的圆半径相同，所以排除A,B,再看C,D，C的圆心是（-3,2），D的圆心是（3，-2）。若想成为题目中所谈到圆的对称圆，这个圆的圆心和题目中圆的圆心的连线的中点必须在直线2x-y+3=o上，C中的圆与题中圆的中点是（-1,1），代入直线，可看出在直线上，D中的圆与题中圆的中点是（2,-1），代入直线，可看出不在直线上。所以答案选C.

Answer 2

Zhu graduated from the Shanghai Ocean Ocean University (formerly Shanghai Fisheries University), is the class of 2001 International Trade school students. In the school's Web site, the reporter found the seven ocean-related news and Zhu. Zhu ocean where there is one pair of interview reports,mac blush, the article that describes him: 1, and the total score of 1370 +5; June 2004 in the National College English Contest, ranked number one, won the first prize. During graduate student, who lived next door to the bedroom in a marine Zhu student said: very reason (of course now does not seem to say how many people will agree), ability, personality moderate. Zhu Ocean It seems the Beisi Ke, Zhu ocean is a very polite young man.

Zhu said a friend of the sea, in the murder case came to light 10 days before his death, Zhu Marine has told him that he liked the new Yang. This friend is also a marine Zhu Virginia Tech students. He declined to be named, said:

school spokesman Larry Link, said the police are not prepared to reveal more details of their relationship.

In addition, police also found a new room Yang, a cell phone, a diary, a letter is not sent. Search results based on tagging, sealing the letter a But the police did not disclose the letter's recipient was.

□ Morning News reporter Xu Huifen

Zhu Ocean once said, Zhu ocean from the room the police took the following items: kitchen knife wrapping paper, digital cameras, medical information manuals. In the new room Yang, police found Young to open the $ 40 to check for Zhu ocean. Have claimed that the new arrival Yang University of Virginia's first few days, life has been a great ocean to take care of Zhu.

Engineering Education Virginia Tech assistant Kensi Tan Teng said that Zhu Ocean can not be the school's assistant.

1 23,Mac cosmetics, U.S. police on January 21 murders at Virginia Tech in the home of the deceased and the suspect were investigated, and further confirmed the relationship between the two met. According to friends of his suspect, the suspect Zhu sent that to the dead marine Yang Xin (sound) have a good impression,

another Virginia Tech University, also believes that Chinese students named Li, Zhu ocean is a gentle person. >
Another reporter was informed that the new Young female students were killed funeral will be held in China. Virginia Tech said it would seek the views of the deceased's family to see if there is a need to do a memorial service in the United States. At present, the Chinese Embassy staff have been rushed to Blacksburg to meet relevant personnel matter in consultation with the University.

suspects had won the first prize

U.S. local time at 19 o'clock on January 21 about the Virginia Tech Graduate Life Center Cafe homicide occurred, the new Chinese female students were beheaded Yang. Police arrested the suspect on the spot Zhu marine and charged with first-degree murder,mac cosmetics outlet, and prohibits bail.

Victims Yang Xin (Xin Yang, transliteration) from Beijing, aged 22, Jan. 8 just arrived in the Virginia Tech Study accounting
suspects Zhu Ocean (Haiyang Zhu, transliteration), aged 25, to from Ningbo, China, in 2008 fall semester, at Virginia Tech University to pursue a doctorate in agricultural and applied economics