Nullspace of a 4×5 matrix via its SVD

Returning to this example, involving a matrix with row size m=4 and column size n=5, and of rank r=3. The nullspace is the span of the last n-r=2 columns of the 5 \times 5 matrix V: \mathbf{N}(A)=\operatorname{span}\left(v_4, v_5\right), with

    \[v_4:=\left(\begin{array}{l} 0 \\ 0 \\ 0 \\ 1 \\ 0 \end{array}\right), \quad v_5:=\left(\begin{array}{c} -\sqrt{0.8} \\ 0 \\ 0 \\ 0 \\ \sqrt{0.2} \end{array}\right)\]

We can check that A v_4=A v_5=0.

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Hyper-Textbook: Optimization Models and Applications Copyright © by L. El Ghaoui. All Rights Reserved.

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