Denote by the set of all 2×2 matrices with real number entries. Let and let .

Determine whether or not each of the following matrices is in .

- : yes, since this matrix is simply again.
- : no, since but .
- : yes, since anything times the zero matrix is again the zero matrix.
- : no, since but .
- : yes, since this is the 2×2 identity matrix.
- : no, since but .

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## Comments

Muchas gracias por el tiempo de escribir esto y explicarlo tan claro.