Question

If $(2,0)$ is the vertex and $y-$ axis the directrix of a parabola,find the coordinates of focus.

• A. Focus is $(2,0)$
• B. Focus is $(4,0)$
• C. Focus is $(8,0)$
• D. Focus is $(-4,0)$

Answer 1

The correct option is B Focus is $(4,0)$

Distance of vertex from directrix $y-$ axis is $2$ and we know it
is half the distance of focus from directrix.
$\therefore$ Focus is $(4,0).$