Question

If the vertex and focus of a parabola are (3,6) and (4,5) then the equation of its directrix is

• A. x-y+7=0
• B. x-y+9=0
• C. x-y+5=0
• D. x-y+3=0

Answer 1

The correct option is C

x-y+5=0

$A=(3,6),S=(4,5)$ and we know $Z=2A-S=(2,7)$
slope of perpendicular of AS=1

Eqn of Directrix

y-7=1(x-2)

$\Rightarrow x-y+5=0$