The focus of parabola is (0, -3) which lies on y-axis. Directrix of the parabola is y - 3 = 0 which is parallel to x-axis.
∴ The equation of the parabola is of the standard form ...(i)
Focus is (0, -a) (0, -3) and directrix y - a = 0 is y - 3 = 0 a = 3
Hence, form (i), the equation of the parabola is
Alternative method:
Let l be the directrix with equation y - 3 = 0.
S (0, -3) is the focus.
Take a point on the parabola. From P, draw PM perpendicular on the directrix l and join PS. By definition of parabola, PS = PM
Hence, the equation of locus of P i.e, equation of parabola is
An equilateral triangle is inscribed in the parabola , where one vertex is at the vertex of the parabola. Find (a) the length of the side of the triangle, (b) area of triangle ABC.