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By applying the definition of product between two square matrices, we find that [tex]\vec A \,\cdot \,\vec A = \left[\begin{array}{cc}1&2\\3&6\end{array}\right] \cdot \left[\begin{array}{cc}1&2\\3&6\end{array}\right][/tex] is equal to the matrix [tex]\vec A \,\cdot \,\vec A = \left[\begin{array}{cc}7&14\\21&42\end{array}\right][/tex]. (Correct choice: D)
In this question we must use the definition of product between two square matrices to determine the resulting construction:
[tex]\vec A \,\cdot \,\vec A = \left[\begin{array}{cc}1&2\\3&6\end{array}\right] \cdot \left[\begin{array}{cc}1&2\\3&6\end{array}\right][/tex]
[tex]\vec A \,\cdot \,\vec A = \left[\begin{array}{cc}7&14\\21&42\end{array}\right][/tex]
By applying the definition of product between two square matrices, we find that [tex]\vec A \,\cdot \,\vec A = \left[\begin{array}{cc}1&2\\3&6\end{array}\right] \cdot \left[\begin{array}{cc}1&2\\3&6\end{array}\right][/tex] is equal to the matrix [tex]\vec A \,\cdot \,\vec A = \left[\begin{array}{cc}7&14\\21&42\end{array}\right][/tex].
To learn more on matrices: https://brainly.com/question/11367104
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