Engineering
Mathematics
Introduction to Matrix
Algebra of Matrices
Multiplication of Matrices
Question

Let p be a non-singular matrix, 1 + p + p2 + .... + pn = 0 (0 denotes the null matrix) then p–1 =

– pn

– (1 + p +...+ pn)

none

pn

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Solution
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Given :

1 + p + p2 ...... pn = 0

applying sum of AP formula

 1. pn+1IpI=0        {I = Identity matrix}

∴ pn+1 = I.

⇒  p. p = I

⇒ pn . pp–1 = I . p–1 (post multiplication with p–1)

⇒  p2 = p–1

⇒ A is correct.