Skip to main contentSkip to solution

A=[01312x231]A=\begin{bmatrix} 0 & 1 & 3 \\ 1 & 2 & x \\ 2 & 3 & 1 \end{bmatrix} and 2B=[1−85−16−312y1]2B=\begin{bmatrix} 1 & -8 & 5 \\ -1 & 6 & -3 \\ 1 & 2y & 1 \end{bmatrix}. If A=B−1A=B^{-1} then x+yx+y is equal to

Solution

✅ Correct Option: 1

A=B−1A = B^{-1} means AB=IAB = I, so A(2B)=2IA(2B) = 2I.

The (1,2)(1,2) entry gives 6+6y=06 + 6y = 0, so y=−1y = -1.

The (2,1)(2,1) entry gives 1−2+x=01 - 2 + x = 0, so x=1x = 1.

These values satisfy all remaining entries, hence x+y=0x + y = 0.

Keyboard Shortcuts

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