Update linear-maps.tex

no need for a "\" in front of the last x in: I can rewrite $\vec{v}$ as $x_1\vec{e_1}+x_2\vec{e_2}+x_3\vec{e_3}+...+\x_n\vec{e_n}$
Merge pull request #16 from onelinelernen/patch-2

Update linear-maps.tex