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AP EAMCET · Maths · Matrices

If A=pqrrpqqrp and AAT=I, then p3+q3+r3=

  1. A ±1
  2. B pqr
  3. C 3pqr
  4. D 3pqr±1
Verified Solution

Answer & Solution

Correct Answer

(D) 3pqr±1

Step-by-step Solution

Detailed explanation

It is given that, AA⊤=I It is an orthogonal matrix and the determinant of orthogonal matrix is ±1 . . pqrrpqqrp=±1 Solve the above determinant, p3-pqr-pqr-pqr+q3+r3=±1 ⇒p3+q3+r3-3pqr=±1 ⇒p3+q3+r3=3pqr±1