Q28 of 63 Page 202

Find the equation of each of the following parabolas

Directrix x = 0, focus at (6, 0)

the distance of any point on the parabola from its focus and its directrix is same.


Given that, directrix, x = 0 and focus = (6, 0)


If a parabola has a vertical axis, the standard form of the equation of the parabola is (x - h)2 = 4p(y - k), where p≠ 0.


The vertex of this parabola is at (h, k).


The focus is at (h, k + p) & the directrix is the line y = k - p.


As the focus lies on x – axis,


Equation is y2 = 4ax or y2 = -4ax


So, for any point P(x, y) on the parabola


Distance of point from directrix = Distance of point from focus


x2 = (x – 6)2 + y2


x2 = x2 - 12x + 36 + y2


y2 - 12x + 36 = 0


Hence the required equation is y2 - 12x + 36 = 0.


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