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**THE PROBLEM**The dot product is:

[tex]\overrightarrow{x}\,=\,\left[ \begin{array}{c} x_1 \\ x_2 \\ \vdots \\ x_n \end{array} \right][/tex]

[tex]\overrightarrow{y}\,=\,\left[ \begin{array}{c} y_1 \\ y_2 \\ \vdots \\ y_n \end{array} \right][/tex]

in [tex]\mathbb{R}^n[/tex]:

[tex]\overrightarrow{x}\,\cdot\,\overrightarrow{y}\,=\,x_1\,y_1\,+\,x_2\,y_2\,+\,\ldots\,+\,x_n\,y_n[/tex]

If the scalar [itex]\overrightarrow{x}\,\cdot\,\overrightarrow{y}[/itex] is equal to zero, the vectors are perpendicular.

Find all vectors in [itex]\mathbb{R}^3[/itex] that are perpendicular to

[tex]\left[ \begin{array}{c} 1 \\ 3 \\ -1 \end{array} \right][/tex].

Draw a sketch as well.

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**MY WORK SO FAR**[tex]\left[ \begin{array}{c} 1 \\ 3 \\ -1 \end{array} \right]\,\cdot\,\left[ \begin{array}{c} x \\ y \\ z \end{array} \right]\,=\,0[/tex]

[tex]x\,+\,3\,y\,-\,z\,=\,0[/tex]

[tex]z\,=\,x\,+\,3\,y[/tex]

Let s = x and t = y

[tex]z\,=\,s\,+\,3\,t[/tex]

[tex]\left[ \begin{array}{c} 1 \\ 3 \\ -1 \end{array} \right]\,\cdot\,\left[ \begin{array}{c} s \\ t \\ s\,+\,3\,t \end{array} \right]\,=\,0[/tex]

Does the above look right?

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