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Determine which sets in Exercise 15-20 are bases for \[{\mathbb{R}^{\bf{2}}}\] or \[{\mathbb{R}^{\bf{3}}}\]. Justify your each answer.

15. \[\left[ {\begin{array}{*{20}{c}}{\bf{5}}\\{ - {\bf{2}}}\end{array}} \right],\left[ {\begin{array}{*{20}{c}}{{\bf{10}}}\\{ - {\bf{3}}}\end{array}} \right]\]

Short Answer

Expert verified

The set \[\left[ {\begin{array}{*{20}{c}}5\\{ - 2}\end{array}} \right],\left[ {\begin{array}{*{20}{c}}{10}\\{ - 3}\end{array}} \right]\] is a basis for \[{\mathbb{R}^2}\]

Step by step solution

01

Find the determinant

Let \[A = \left[ {\begin{array}{*{20}{c}}5&{10}\\{ - 2}&{ - 3}\end{array}} \right]\]. Then,

\[\begin{array}{c}\det A = 5\left( { - 3} \right) - 10\left( { - 2} \right)\\ = - 15 + 20\\\det A = 5 \ne 0\end{array}\]

This implies that A is invertible.

02

Use the inverse matrix theorem

Here, A is invertible. This implies that the columns of A form alinearly independent set, and the columns span \[{\mathbb{R}^2}\] by using statements (a), (e), and (h) in the inverse matrix theorem.

03

Conclusion

Hence, the columns of A \[\left[ {\begin{array}{*{20}{c}}5\\{ - 2}\end{array}} \right],\left[ {\begin{array}{*{20}{c}}{10}\\{ - 3}\end{array}} \right]\] form a basis for \[{\mathbb{R}^2}\].

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