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Mathematics
Problem
Let
A
=
(
1
0
k
2
1
1
0
1
1
)
A=\begin{pmatrix}1&0&k\\2&1&1\\0&1&1\end{pmatrix}
A
=
1
2
0
0
1
1
k
1
1
with
k
≠
0
k\neq0
k
=
0
. For which value of
k
k
k
does the element in the second row and first column of
A
−
1
A^{-1}
A
−
1
equal
−
1
-1
−
1
? a)
k
=
−
1
k=-1
k
=
−
1
b)
k
=
2
k=2
k
=
2
c)
k
=
1
k=1
k
=
1
d)
k
=
1
2
k=\dfrac12
k
=
2
1
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