The vertex is v(-1,3) , focus is f(-1,8) and the equation of directrix is y = -2.
What is a parabola?
A parabola is a plane curve generated by a point moving so that its distance from a fixed point is equal to its distance from a fixed line. The equidistant from a fixed point called the focus (F), and the fixed-line is called the directrix (x + a = 0).
For the given situation,
The standard form of equation of parabola is given by, [tex]y=\frac{1}{4p}(x-h)^{2}+k[/tex]
The vertex is given by [tex]v(h,k)[/tex]
The focus is given by [tex]f(h,k-p)[/tex]
The equation of directrix is given by [tex]y=k+p[/tex]
The given equation is [tex](x+1)^{2} =-20(y-3)[/tex]
On rearranging the given equation in standard form,
⇒ [tex](x+1)^{2} =-20y+60[/tex]
⇒ [tex](x+1)^{2} -60=-20y[/tex]
Divide by 20 on both sides,
⇒ [tex]\frac{(x+1)^{2}}{20} +4 = y[/tex]
⇒ [tex]y=\frac{-1}{(4)(5)} (x+1)^{2} +3[/tex]
On comparing the above equation with the standard form,we get
[tex]p=-5, h=-1, k=3[/tex]
⇒ [tex]k-p=3-(-5)\ =8[/tex]
Hence we can conclude that the vertex is v(-1,3), focus is f(-1,8) and equation of directrix is y=-2.
Learn more about a parabola here
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