1.

Find the vertex, focus, axis, directrix, and the length of the latus rectum of the parabola y2 – 8y – 8x + 24 = 0.

Answer»

y2 – 8y – 8x + 24 = 0 

⇒ y2 – 8y – 42 = 8x – 24 + 42 

⇒ (y – 4)2 = 8x – 8 

⇒ (y – 4)2 = 8(x – 1) 

⇒ (y – 4)= 4(2) (x – 1) 

∴ a = 2

Y2 = 4(2)X where X = x – 1 and Y = y – 4

X, Y coordinatesx, y coordinates
Vertex (0,0)X = 0, Y = 0x - 1 = 0, y - 4 = 0 (1,4)
(1,4)
Focus (a,0)X = 2, Y = 0x - 1 = 2, y - 4 = 0 
x = 2 + 1 = 3, y = 4
(3,4)
Axis 
x-axis
Y = 0 y - 4 = 0, y = 4
Directrix
x + a = 0 
X + 2 = 0 x - 1 + 2 = 0
x + 1 = 0 
x = - 1
Length of latus rectum4a = 8


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