Physics I / Eigenvalues and Eigenvectors
Practice question · Multiple choice

A transformation stretches the plane. Vector v0v \ne 0 satisfies Av=3vAv = 3v. What is geometrically special about vv’s direction?

Hints
  1. 3v3v points the same way as vv, only longer.
  2. Most vectors get knocked off their line by a transformation. Eigenvectors are the stubborn ones that stay on theirs.
Show the answer

B. The transformation keeps that direction fixed, stretching 3×

Why

Eigenvectors mark the invariant axes of a transformation, the directions it cannot turn, only rescale (by the eigenvalue). Finding them reveals a transformation’s skeleton: along those axes, matrix action reduces to simple multiplication.

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