Chapter 2: Q2.9-20E (page 93)
In Exercises 19-24, justify each answer or construction.
What is the rank of a \({\bf{4}} \times {\bf{5}}\) matrix whose null space in three dimensional.
Short Answer
The dimension of the null space of A is 2.
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Chapter 2: Q2.9-20E (page 93)
In Exercises 19-24, justify each answer or construction.
What is the rank of a \({\bf{4}} \times {\bf{5}}\) matrix whose null space in three dimensional.
The dimension of the null space of A is 2.
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Solve the Leontief production equation for an economy with three sectors, given that
\(C = \left[ {\begin{array}{*{20}{c}}{.2}&{.2}&{.0}\\{.3}&{.1}&{.3}\\{.1}&{.0}&{.2}\end{array}} \right]\)and \({\mathop{\rm d}\nolimits} = \left[ {\begin{array}{*{20}{c}}{40}\\{60}\\{80}\end{array}} \right]\).
Find the inverses of the matrices in Exercises 29–32, if they exist. Use the algorithm introduced in this section.
29. \(\left( {\begin{aligned}{*{20}{c}}1&2\\4&7\end{aligned}} \right)\)
Suppose \(AD = {I_m}\) (the \(m \times m\) identity matrix). Show that for any b in \({\mathbb{R}^m}\), the equation \(A{\mathop{\rm x}\nolimits} = {\mathop{\rm b}\nolimits} \) has a solution. (Hint: Think about the equation \(AD{\mathop{\rm b}\nolimits} = {\mathop{\rm b}\nolimits} \).) Explain why Acannot have more rows than columns.
In Exercises 1 and 2, compute each matrix sum or product if it is defined. If an expression is undefined, explain why. Let
\(A = \left( {\begin{aligned}{*{20}{c}}2&0&{ - 1}\\4&{ - 5}&2\end{aligned}} \right)\), \(B = \left( {\begin{aligned}{*{20}{c}}7&{ - 5}&1\\1&{ - 4}&{ - 3}\end{aligned}} \right)\), \(C = \left( {\begin{aligned}{*{20}{c}}1&2\\{ - 2}&1\end{aligned}} \right)\), \(D = \left( {\begin{aligned}{*{20}{c}}3&5\\{ - 1}&4\end{aligned}} \right)\) and \(E = \left( {\begin{aligned}{*{20}{c}}{ - 5}\\3\end{aligned}} \right)\)
\( - 2A\), \(B - 2A\), \(AC\), \(CD\).
Suppose P is invertible and \(A = PB{P^{ - 1}}\). Solve for Bin terms of A.
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