AAKASH AITS 14( maths )

A is an orthogonal matrix of odd ordeer such that |A|(x2+x+1) > 0, x belongs R.
If I is a unit matrix of the same order as of A then value of |A(I+A2)-(I+A)(I+A2-A)| is equal to

A) 1 B) -1
C) 0 D) 2

4 Answers

106
Asish Mahapatra ·

I got (C)

the final expression was coming as |A-I|..

I took the matrix \begin{bmatrix} 1 & 0 & 0\\ 0 & 1 & 0\\ 0 & 0 & 1 \end{bmatrix}
for considering the answer

1
Manmay kumar Mohanty ·

culd u post full solution............
after cnsidering I = as u mentioned wat to do next ............[7][7]

106
Asish Mahapatra ·

for orthogonal matrix A2=A
=> |A| = 0,±1

but as |A|(x2+x+1) > 0
=> |A| = 1

the exp. given is

|A(I+A) - (I+A)(I+A-A)| (as A2=A)
= | A + A2 - I - A|
= |A-I|

then i took A = I (as I is also orthogonal with |A| = 1)

we get |I-I| = 0

but m not entirely convinced abt my solution

1
Manmay kumar Mohanty ·

ok thnks for that ASISH

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