2010015707

Given vectors $\overrightarrow{a}=(-1;2;1)$, $\overrightarrow{b}=(0;-1;1)$, and $\overrightarrow{c}=(-2;0;1)$, find the length of the vector $\overrightarrow{u}=\overrightarrow{a}-2\overrightarrow{b}+\overrightarrow{c}$.