ParabolaHard

Question

A parabola passes through (1, 2) and (3, 4). The tangents drawn at these points intersect at (-6, 8), then the slope of directrix of the parabola is

Options

A.5/8
B.-5/8
C.8/5
D.-8/5

Solution

As the line joining the mid point of the chord joining (1, 2), (3, 4) and the point of intersection of tangents at these points is parallel to axis of parabola
∴  Slope of axis =
∴  Slope of directrix =

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