Q. 35.0( 1 Vote )
Write the equation of the directrix of the parabola x2 – 4x – 8y + 12 = 0
Answer :
Given equation of the parabola is x2 - 4x - 8y + 12 = 0
⇒ x2 - 4x + 12 = 8y
⇒ x2 - 4x + 4 = 8y - 8
⇒ (x - 2)2 = 8(y - 1)
Comparing with the standard form of parabola (x - a)2 = 4b(y - c) we get,
⇒ 4b = 8
⇒ b = 2
⇒ The equation of the directrix is y - c = - b
⇒ Directrix is y - 1 = - 2
⇒ Directrix is y = - 2 + 1
⇒ Directrix is y = - 1
∴The equation of the directrix is y = - 1.
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