ParabolaHard
Question
If the line x - 1 = 0 is the directrix of the parabola y2 = kx - 8, then one of the values of k is
Options
A.
B.8
C.4
D.
Solution
Given, y2 = kx - 8
⇒
Shifting the origin Y2 = kX where Y = y, X = x - 8 / k
Directrix of standard parabola is
Directrix of original parabola is
Now, x =1 also coincides with
On solving, we get k = 4
⇒
Shifting the origin Y2 = kX where Y = y, X = x - 8 / k
Directrix of standard parabola is
Directrix of original parabola is
Now, x =1 also coincides with
On solving, we get k = 4
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