21) Goi duong tron (C) co tam I (\(\dfrac{1}{2}\);1) va ban kinh R = 3. Phuong trinh nao sau day la phuong trinh anh cua duong tron (C) qua phep tinh tien theo vecto \(\overrightarrow{a}=\left(\dfrac{-1}{2};3\right)\)A. x2 + y2 -4y - 5 = 0 B. x2 + y2 - 4y + 1 = 0 C. x2 + y2 + 4y - 5 = 0 D. x2 + y2 - 4y + 5 =...
Đọc tiếp
21) Goi duong tron (C) co tam I (\(\dfrac{1}{2}\);1) va ban kinh R = 3. Phuong trinh nao sau day la phuong trinh anh cua duong tron (C) qua phep tinh tien theo vecto \(\overrightarrow{a}=\left(\dfrac{-1}{2};3\right)\)
A. x2 + y2 -4y - 5 = 0 B. x2 + y2 - 4y + 1 = 0 C. x2 + y2 + 4y - 5 = 0 D. x2 + y2 - 4y + 5 = 0
Ta có:
I'=(1/2+(-1/2);1+3)=(0;4) => X^2 -(y-4)^2=3^2 <=> x^2 - (y^2-8y+16)=9 <=> x^2 -y^2 +8y -16-9=0. <=> x^2 - y^2 +8y - 25 =0
Chọn D