Skip to content
Part CCSIR NET December 2024positive-definite-says-nothing-about-this-basis

Positive definite says nothing about this basis

Let V be a two-dimensional real vector space with a basis {}. Let be a symmetric bilinear form. Let . Which of the following statements are necessarily true?

  1. A..
  2. B.If r = s = t, then either f(v, v) ≥ 0 for all v ∈ V or f(v, v) ≤ 0 for all v ∈ V.
  3. C.If f is positive definite, then r ≠ s, s ≠ t and r ≠ t.
  4. D.If f is positive definite, then .

You have the answer. Trap Analysis is why the other three were written.

Not a worked solution repeated four times — the specific reasoning error each wrong option was built to reward.

See pricing

50 are analysed free — try those first.

Related counterexample: Every real symmetric matrix is positive definite if det > 0

More on this topic

The chapter behind this: Quadratic forms, signature and definiteness — free to read

From Inner Product Spaces and FormsQuadratic forms, positive definiteness, Sylvester's law

ShareWhatsAppTelegram