If `A=[a b0a]` is nth root of `I_2,` then choose the correct statements: If `n` is odd, `a=1,b=0` If `n` is odd, `a=-1,b=0` If `n` is even, `a=1,b=0`
If `A=[a b0a]`
is nth root of `I_2,`
then choose the correct statements:
If `n`
is odd, `a=1,b=0`
If `n`
is odd, `a=-1,b=0`
If `n`
is even, `a=1,b=0`
If `n`
is even, `a=-1,b=0`
a. i, ii, iii, iv b.
ii, iii, iv
c. i, ii, iii, iv d. i,
iii, iv
A. i, ii, iii
B. ii, iii, iv
C. i, ii, iii, iv
D. i, iii, iv
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1 Answers
Correct Answer - D
If A is nth root of `I_(2)`, then `A^(n)=I_(2)`. Now,
`A^(2)=[(a,b),(0,a)][(a,b),(0,a)]=[(a^(2),2ab),(0,a^(2))]`
`A^(3)=A^(2) A=[(a^(2),2ab),(0,a^(2))][(a,b),(0,a)]=[(a^(3),3a^(2)b),(0,a^(3))]`
Thus, `A^(n)=[(n^(n),na^(n-1)b),(0,a^(n))]`
Now,
`A^(n)=I implies [(a^(n),na^(n-1)b),(0,a^(n))]=[(1,0),(0,1)]`
`implies a^(n)=1, b=0`
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Answered