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TS EAMCET · Maths · Matrices

If \(\mathrm{P}\) is a non-singular matrix such that \(\mathrm{I}+\mathrm{P}+\mathrm{P}^2 \ldots+\mathrm{P}^{\mathrm{n}}=\) \(0(0\) denotes the null matrix \()\), then \(\mathrm{P}^{-1}=\)

  1. A \(\mathrm{P}^{\mathrm{n}}\)
  2. B \(-\mathrm{P}^{\mathrm{n}}\)
  3. C \(-\left(1+P+\ldots+P^n\right)\)
  4. D \(-\left(1+P+\ldots+P^{n-1}\right)\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\mathrm{P}^{\mathrm{n}}\)

Step-by-step Solution

Detailed explanation

\(I+P+P^2+\ldots . .+P^n=0... (i)\) \(\left(I+P+P^2+\ldots . .+P^{n-1}\right)=0-P^n=-P^n\) Pre multiply (i) with \(P^{-1}\) \(\begin{aligned} & P^{-1}+I+P+P^2+\ldots . .+P^{n-1}=0 \\ & P^{-1}=0-\left(I+P+P^2+\ldots .+P^{n-1}\right) \Rightarrow P^{-1}=P^n \end{aligned}\)