Skip to main contentSkip to solution

If A=[0xx2yy−yz−zz]A = \begin{bmatrix} 0 & x & x \\ 2y & y & -y \\ z & -z & z \end{bmatrix} such that AAT=2IAA^T=2I (where I is an identity matrix of order 3), then which of the following are True?

A. x2=1,3y2=2x^2=1, 3y^2=2

B. 6y2=4,2z2=36y^2=4, 2z^2=3

C. 9z2=6,x2=19z^2=6, x^2=1

D. x2:y2:z2=3:1:2x^2:y^2:z^2 = 3:1:2

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 3

Each diagonal entry of AATAA^T is the squared length of a row and must equal 22.

Row 1: 2x2=22x^2=2, so x2=1x^2=1. Row 2: 6y2=26y^2=2, so y2=13y^2=\frac{1}{3}. Row 3: 3z2=23z^2=2, so z2=23z^2=\frac{2}{3}.

Hence 9z2=69z^2=6 (C holds) and x2:y2:z2=1:13:23=3:1:2x^2:y^2:z^2=1:\frac{1}{3}:\frac{2}{3}=3:1:2 (D holds), while A and B fail.

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question