Equation of Parabola When Its Axis Is Parallel to X or Y Axis
If a focal ch...
Question
If a focal chord of the parabola y2=bx is 2x−y−8=0, then the equation of the directrix is
A
y+4=0
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B
x−4=0
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C
y−4=0
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D
x+4=0
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Solution
The correct option is Dx+4=0 Focal chord of parabola y2=bx always passes through its focus which is (b4,0)
Now it satisfies 2x−y−8=0 ∴2b4−0−8⇒b=16
Hence, parabola will be y2=16x ∴a=4 ∵ Directrix is x+a=0, ⇒x+4=0