<exercise checkit-seed="0011" checkit-slug="V2" checkit-title="Linear combinations">
<statement>
<p>Consider the following statement.</p>
<ul>
<li>
The vector <m> \left[\begin{array}{c}
-6 \\
-8 \\
-4 \\
4
\end{array}\right] </m>is not
a linear combination of the vectors <m> \left[\begin{array}{c}
-4 \\
0 \\
-3 \\
-2
\end{array}\right] , \left[\begin{array}{c}
-3 \\
0 \\
-1 \\
1
\end{array}\right] , \left[\begin{array}{c}
7 \\
0 \\
4 \\
1
\end{array}\right] , \text{ and } \left[\begin{array}{c}
-2 \\
0 \\
-4 \\
-6
\end{array}\right] </m>.
</li>
</ul>
<ol>
<li> Write an equivalent statement using a vector equation.</li>
<li> Explain why your statement is true or false.</li>
</ol>
</statement>
<answer>
<me>\operatorname{RREF} \left[\begin{array}{cccc|c}
-4 & -3 & 7 & -2 & -6 \\
0 & 0 & 0 & 0 & -8 \\
-3 & -1 & 4 & -4 & -4 \\
-2 & 1 & 1 & -6 & 4
\end{array}\right] = \left[\begin{array}{cccc|c}
1 & 0 & -1 & 2 & 0 \\
0 & 1 & -1 & -2 & 0 \\
0 & 0 & 0 & 0 & 1 \\
0 & 0 & 0 & 0 & 0
\end{array}\right] </me>
<ol>
<li>
The vector equation <m> x_{1} \left[\begin{array}{c}
-4 \\
0 \\
-3 \\
-2
\end{array}\right] + x_{2} \left[\begin{array}{c}
-3 \\
0 \\
-1 \\
1
\end{array}\right] + x_{3} \left[\begin{array}{c}
7 \\
0 \\
4 \\
1
\end{array}\right] + x_{4} \left[\begin{array}{c}
-2 \\
0 \\
-4 \\
-6
\end{array}\right] = \left[\begin{array}{c}
-6 \\
-8 \\
-4 \\
4
\end{array}\right] </m>has no solutions.</li>
<li>
<p><m> \left[\begin{array}{c}
-6 \\
-8 \\
-4 \\
4
\end{array}\right] </m> is not
a linear combination of the vectors <m> \left[\begin{array}{c}
-4 \\
0 \\
-3 \\
-2
\end{array}\right] , \left[\begin{array}{c}
-3 \\
0 \\
-1 \\
1
\end{array}\right] , \left[\begin{array}{c}
7 \\
0 \\
4 \\
1
\end{array}\right] , \text{ and } \left[\begin{array}{c}
-2 \\
0 \\
-4 \\
-6
\end{array}\right] </m>.
</p>
</li>
</ol>
</answer>
</exercise>