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If A=[{:(2,7),(1,5):}] then that is A + ...

If `A=[{:(2,7),(1,5):}]` then that is A + `3A^(-1)` equal to ?

A

3 I

B

5 I

C

7 I

D

None of these

Text Solution

Verified by Experts

The correct Answer is:
C
`A=[(2,7),(1,5)]`
Now, `A^(-1)=(1)/(|A|)adj(A)`
`=(1)/((10-7))[(5,-7),(-1,2)]`
`=(1)/(3)[(5,-7),(-1,2)]`
`rArr" "3A^(-1)=[(5,-7),(-1,2)]`
Now, `A+3A^(-1)=[(2,7),(1,5)]+[(5,-7),(-1,2)]`
`=[(7,0),(0,7)]=7[(1,0),(0,1)]=7I` where I is Identity Matrix.
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