<item ident="A4-0009" title="A4 | Injectivity and surjectivity | ver. 0009">
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<div class="exercise-statement"><p><strong>A4.</strong></p> Let <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?T:\mathbb{R}^ 4 \to \mathbb{R}^ 4" alt="T:\mathbb{R}^ 4 \to \mathbb{R}^ 4" title="T:\mathbb{R}^ 4 \to \mathbb{R}^ 4" data-latex="T:\mathbb{R}^ 4 \to \mathbb{R}^ 4"/> be the linear transformation given by the standard matrix <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?\left[\begin{array}{cccc} 1 & 0 & 3 & 3 \\ 0 & 1 & -3 & 5 \\ 1 & 0 & 3 & 4 \\ 0 & -2 & 6 & -7 \end{array}\right] ." alt="\left[\begin{array}{cccc} 1 & 0 & 3 & 3 \\ 0 & 1 & -3 & 5 \\ 1 & 0 & 3 & 4 \\ 0 & -2 & 6 & -7 \end{array}\right] ." title="\left[\begin{array}{cccc} 1 & 0 & 3 & 3 \\ 0 & 1 & -3 & 5 \\ 1 & 0 & 3 & 4 \\ 0 & -2 & 6 & -7 \end{array}\right] ." data-latex="\left[\begin{array}{cccc} 1 & 0 & 3 & 3 \\ 0 & 1 & -3 & 5 \\ 1 & 0 & 3 & 4 \\ 0 & -2 & 6 & -7 \end{array}\right] ."/><ol type="a"><li>Explain why <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?T" alt="T" title="T" data-latex="T"/> is or is not injective.</li><li>Explain why <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?T" alt="T" title="T" data-latex="T"/> is or is not surjective.</li></ol></div>
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<mattext texttype="text/html"><div class="exercise-statement">
<p><strong>A4.</strong></p> Let <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?T:%5Cmathbb%7BR%7D%5E%204%20%5Cto%20%5Cmathbb%7BR%7D%5E%204" alt="T:\mathbb{R}^ 4 \to \mathbb{R}^ 4" title="T:\mathbb{R}^ 4 \to \mathbb{R}^ 4" data-latex="T:\mathbb{R}^ 4 \to \mathbb{R}^ 4"> be the linear transformation given by the standard matrix <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7D%201%20&amp;%200%20&amp;%203%20&amp;%203%20%5C%5C%200%20&amp;%201%20&amp;%20-3%20&amp;%205%20%5C%5C%201%20&amp;%200%20&amp;%203%20&amp;%204%20%5C%5C%200%20&amp;%20-2%20&amp;%206%20&amp;%20-7%20%5Cend%7Barray%7D%5Cright%5D%20." alt="\left[\begin{array}{cccc} 1 &amp; 0 &amp; 3 &amp; 3 \\ 0 &amp; 1 &amp; -3 &amp; 5 \\ 1 &amp; 0 &amp; 3 &amp; 4 \\ 0 &amp; -2 &amp; 6 &amp; -7 \end{array}\right] ." title="\left[\begin{array}{cccc} 1 &amp; 0 &amp; 3 &amp; 3 \\ 0 &amp; 1 &amp; -3 &amp; 5 \\ 1 &amp; 0 &amp; 3 &amp; 4 \\ 0 &amp; -2 &amp; 6 &amp; -7 \end{array}\right] ." data-latex="\left[\begin{array}{cccc} 1 &amp; 0 &amp; 3 &amp; 3 \\ 0 &amp; 1 &amp; -3 &amp; 5 \\ 1 &amp; 0 &amp; 3 &amp; 4 \\ 0 &amp; -2 &amp; 6 &amp; -7 \end{array}\right] ."><ol type="a">
<li>Explain why <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?T" alt="T" title="T" data-latex="T"> is or is not injective.</li>
<li>Explain why <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?T" alt="T" title="T" data-latex="T"> is or is not surjective.</li>
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<response_label ident="answer1" rshuffle="No"/>
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<h4>Partial Answer:</h4>
<p>
<p style="text-align:center;">
<img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?\operatorname{RREF} \left[\begin{array}{cccc} 1 & 0 & 3 & 3 \\ 0 & 1 & -3 & 5 \\ 1 & 0 & 3 & 4 \\ 0 & -2 & 6 & -7 \end{array}\right] = \left[\begin{array}{cccc} 1 & 0 & 3 & 0 \\ 0 & 1 & -3 & 0 \\ 0 & 0 & 0 & 1 \\ 0 & 0 & 0 & 0 \end{array}\right]" alt="\operatorname{RREF} \left[\begin{array}{cccc} 1 & 0 & 3 & 3 \\ 0 & 1 & -3 & 5 \\ 1 & 0 & 3 & 4 \\ 0 & -2 & 6 & -7 \end{array}\right] = \left[\begin{array}{cccc} 1 & 0 & 3 & 0 \\ 0 & 1 & -3 & 0 \\ 0 & 0 & 0 & 1 \\ 0 & 0 & 0 & 0 \end{array}\right]" title="\operatorname{RREF} \left[\begin{array}{cccc} 1 & 0 & 3 & 3 \\ 0 & 1 & -3 & 5 \\ 1 & 0 & 3 & 4 \\ 0 & -2 & 6 & -7 \end{array}\right] = \left[\begin{array}{cccc} 1 & 0 & 3 & 0 \\ 0 & 1 & -3 & 0 \\ 0 & 0 & 0 & 1 \\ 0 & 0 & 0 & 0 \end{array}\right]" data-latex="\operatorname{RREF} \left[\begin{array}{cccc} 1 & 0 & 3 & 3 \\ 0 & 1 & -3 & 5 \\ 1 & 0 & 3 & 4 \\ 0 & -2 & 6 & -7 \end{array}\right] = \left[\begin{array}{cccc} 1 & 0 & 3 & 0 \\ 0 & 1 & -3 & 0 \\ 0 & 0 & 0 & 1 \\ 0 & 0 & 0 & 0 \end{array}\right]"/>
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</p>
<ol type="a">
<li><img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?T" alt="T" title="T" data-latex="T"/> is not injective</li>
<li><img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?T" alt="T" title="T" data-latex="T"/> is not surjective</li>
</ol>
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<mattext texttype="text/html"><div class="exercise-answer">
<h4>Partial Answer:</h4>
<p>
</p>
<p style="text-align:center;">
<img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?%5Coperatorname%7BRREF%7D%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7D%201%20&amp;%200%20&amp;%203%20&amp;%203%20%5C%5C%200%20&amp;%201%20&amp;%20-3%20&amp;%205%20%5C%5C%201%20&amp;%200%20&amp;%203%20&amp;%204%20%5C%5C%200%20&amp;%20-2%20&amp;%206%20&amp;%20-7%20%5Cend%7Barray%7D%5Cright%5D%20=%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bcccc%7D%201%20&amp;%200%20&amp;%203%20&amp;%200%20%5C%5C%200%20&amp;%201%20&amp;%20-3%20&amp;%200%20%5C%5C%200%20&amp;%200%20&amp;%200%20&amp;%201%20%5C%5C%200%20&amp;%200%20&amp;%200%20&amp;%200%20%5Cend%7Barray%7D%5Cright%5D" alt="\operatorname{RREF} \left[\begin{array}{cccc} 1 &amp; 0 &amp; 3 &amp; 3 \\ 0 &amp; 1 &amp; -3 &amp; 5 \\ 1 &amp; 0 &amp; 3 &amp; 4 \\ 0 &amp; -2 &amp; 6 &amp; -7 \end{array}\right] = \left[\begin{array}{cccc} 1 &amp; 0 &amp; 3 &amp; 0 \\ 0 &amp; 1 &amp; -3 &amp; 0 \\ 0 &amp; 0 &amp; 0 &amp; 1 \\ 0 &amp; 0 &amp; 0 &amp; 0 \end{array}\right]" title="\operatorname{RREF} \left[\begin{array}{cccc} 1 &amp; 0 &amp; 3 &amp; 3 \\ 0 &amp; 1 &amp; -3 &amp; 5 \\ 1 &amp; 0 &amp; 3 &amp; 4 \\ 0 &amp; -2 &amp; 6 &amp; -7 \end{array}\right] = \left[\begin{array}{cccc} 1 &amp; 0 &amp; 3 &amp; 0 \\ 0 &amp; 1 &amp; -3 &amp; 0 \\ 0 &amp; 0 &amp; 0 &amp; 1 \\ 0 &amp; 0 &amp; 0 &amp; 0 \end{array}\right]" data-latex="\operatorname{RREF} \left[\begin{array}{cccc} 1 &amp; 0 &amp; 3 &amp; 3 \\ 0 &amp; 1 &amp; -3 &amp; 5 \\ 1 &amp; 0 &amp; 3 &amp; 4 \\ 0 &amp; -2 &amp; 6 &amp; -7 \end{array}\right] = \left[\begin{array}{cccc} 1 &amp; 0 &amp; 3 &amp; 0 \\ 0 &amp; 1 &amp; -3 &amp; 0 \\ 0 &amp; 0 &amp; 0 &amp; 1 \\ 0 &amp; 0 &amp; 0 &amp; 0 \end{array}\right]">
</p>
<ol type="a">
<li>
<img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?T" alt="T" title="T" data-latex="T"> is not injective</li>
<li>
<img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?T" alt="T" title="T" data-latex="T"> is not surjective</li>
</ol>
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