Question

The equation of director circle of the parabola $y^2=10(x-1)$

• A. $x^2+y^2-2 x-4 y+4=0$
• B. $2 x+3=0$
• C. $2 x+5=0$
• D. $x^2+y^2-4 x+2 y+2=0$

Answer 1

Answer: (B)

Director circle of parabola is direcctrix
so $X =- a$
$\Rightarrow x-1=-\frac{5}{2} \Rightarrow 2 x+3=0$