Two lines ax + by + c = 0 and dx + ey + f = 0 are perpe... – Geometry

Geometrymedium · Past Paper

Two lines ax + by + c = 0 and dx + ey + f = 0 are perpendicular if:

Aad + be = 0

Bae + bd = 0

Cab + de = 0

Da/d = b/e

✓ Correct Answer: A — ad + be = 0

Slopes are -a/b and -d/e. Product: (-a/b)(-d/e) = -1 => ad/be = -1 => ad = -be => ad + be = 0.

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