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Mathematics
Problem
Let
A
=
(
1
−
1
2
−
2
)
A = \begin{pmatrix} 1 & -1 \\ 2 & -2 \end{pmatrix}
A
=
(
1
2
−
1
−
2
)
and
B
=
(
1
1
1
1
)
B = \begin{pmatrix} 1 & 1 \\ 1 & 1 \end{pmatrix}
B
=
(
1
1
1
1
)
. Which of the following is correct concerning the products
A
B
AB
A
B
and
B
A
BA
B
A
? a)
A
B
=
B
A
≠
O
AB = BA \neq O
A
B
=
B
A
=
O
b)
A
B
=
O
AB = O
A
B
=
O
and
B
A
=
O
BA = O
B
A
=
O
c)
A
B
=
O
AB = O
A
B
=
O
and
B
A
≠
O
BA \neq O
B
A
=
O
d)
A
B
≠
O
AB \neq O
A
B
=
O
and
B
A
=
O
BA = O
B
A
=
O
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