A=⎡⎢⎣100210321⎤⎥⎦,U1,U2 and U3 are columns matrices satisfying AU1=⎡⎢⎣100⎤⎥⎦,AU2=⎡⎢⎣230⎤⎥⎦,AU3=⎡⎢⎣231⎤⎥⎦ and U is 3×3 matrix whose columns are U1,U2,U3 then answer the following question
The sum of elements of U−1 is
A
-1
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B
0
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C
1
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D
3
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Solution
The correct option is B 0 U=⎡⎢⎣122−2−1−11−4−3⎤⎥⎦ ⇒|U|=−1−14+18=3 Now, adjU=CT=⎡⎢⎣−1−79−2−560−33⎤⎥⎦T ⇒adjU=⎡⎢⎣−1−20−7−5−3963⎤⎥⎦ Hence, U−1=13⎡⎢⎣−1−20−7−5−3963⎤⎥⎦ Now, sum of elements of U−1=0