## Elementary Linear Algebra 7th Edition

The length is $=\sqrt {54}$ units.
Length$=\sqrt {(2)^{2}+(0)^{2}+(-5)^{2}+(5)^{2}}$ $=\sqrt {4+0+25+25}$ $=\sqrt {54}$, since a length must be greater than zero (cannot be negative) Therefore the length is $=\sqrt {54}$ units.