1.

If `A=[(2,-1),(1,3)], then A^(-1)`=?A. `[(3/7,(-1)/7),(1/7,2/7)]`B. `[(3/7,(1)/7),((-1)/7,2/7)]`C. `[(3/7,(1)/7),(1/7,2/7)]`D. none of these

Answer» Correct Answer - B
`|A|=|(2,-1),(1,3)|=(6+1)=7 ne 0`
`M_(11)=3,M_(12)=1,M_(21)=-1 and M_(22)=2`
`therefore C_(11)=3,C_(12)=-1,C_(21)=1 and C_(22)=2`
`rArr AdjA=[(3,-1),(1,2)]=[(3,1),(-1,2)]`
`rArr A^(-1)=1/(|A|)(adjA)=1/7[(3,1),(-1,2)]=[(3/7,1/7),(-1/7,2/7)]`


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