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If `A=[5a-b3 2]`and A adj `A=AA^T`, then `5a+b`is equal to:(1) `-1`(2) 5(3) 4 (4)13A. -1B. 5C. 4D. 13 |
Answer» Correct Answer - B It is given that matrix `{:A=[(5a,-b),(3,2)]:}` satisfies the equation `A(adj A) =A A^T` `rArr absAI_2=A A^T` `rArr (10a+3b){:[(1,0),(0,1)]=[(5a,-b),(3,2)][(5a,3),(-b,2)]:}` `rArr {:[(10a+3b,0),(0,10a+3b)]=[(25a^2+b^2,15a-2b),(15a-2b,13)]:}` `rArr 10a+3b=13,15a-2b=0and 25a^2+b^2=10a+3b` `a=2/5and b=3` `:. 5a+b=2+3=5` |
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