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If A=|[alpha,2], [2,alpha]| and |A|^3=...

If `A=|[alpha,2], [2,alpha]| and |A|^3=125` , then the value of `alpha` is a.`+-1` b. `+-2` c. `+-3` d. `+-5`

A

`pm1`

B

`pm2`

C

`pm3`

D

`pm5`

Text Solution

Verified by Experts

The correct Answer is:
C
We have,
`absA={:abs((alpha,2),(2,alpha))=alpha^2-4:}`
`:. Abs(A^3)=125`
`rArr abs(A)^3=125`
`rArr(alpha-4)^3-125rArr alpha^2=9rArr alpha=pm3`.
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