If $(2,0)$ is the vertex and $Y$-axis is the directrix of a parabola, then its focus is

If $(2,0)$ is the vertex and $Y$-axis is the directrix of a parabola, then its focus is
  1. $(2,0)$
  2. $(-2,0)$
  3. $(4,0)$
  4. $(0,4)$

Solution

Vertex of parabola is $(2,0)$ Directrix of parabola is $x=0$ Vertex is mid-point of focus and origin. $\therefore \quad 2=\frac{a+0}{2}$
$a=4$ $\therefore$ Focus $=(4,0)$

Asked in: AP EAMCET 2021 (24 Aug Shift 2)

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