[tex]\bf PQ\implies \ \textless \ 7-5,3-4\ \textgreater \ \implies \ \textless \ 2,-1\ \textgreater \
\\\\\\
RS\implies \ \textless \ 4-8,1-6\ \textgreater \ \implies \ \textless \ -4,-5\ \textgreater \
\\\\\\
3RS\implies 3\ \textless \ -4,-5\ \textgreater \ \implies \ \textless \ 3\cdot -4,3\cdot -5\ \textgreater \ \implies \ \textless \ -12,-15\ \textgreater \
\\\\\\
\overrightarrow{PQ}+3\overrightarrow{RS}\implies \ \textless \ 2,-1\ \textgreater \ +\ \textless \ -12,-15\ \textgreater \
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\ \textless \ 2-12,-1-15\ \textgreater \ \implies \boxed{\ \textless \ -10,-16\ \textgreater \ }\\\\
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magnitude
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\sqrt{(-10)^2+(-16)^2}\implies \sqrt{100+256}\implies \sqrt{356}\implies \boxed{2\sqrt{89}}[/tex]
