$\because \,\,|2\vec a \,\, - \,\,\vec b |\,\, = \,\,5$
$ \Rightarrow \,\,|2\vec a \,\, - \,\,\vec b {|^2}\,\, = \,\,{5^2}\,\, $
$\Rightarrow \,\,4{a^2}\,\, + \;\,{b^2}\,\, - \,\,4\vec a .\,\vec b \,\, = \,\,25$
$ \Rightarrow \,\,16\,\, + \,\,9\,\, - \,\,4\,\vec a .\,\vec b \,\, = \,\,25\,\,\,$
$\therefore \,\,\vec a .\,\vec b \,\, = \,\,0$
$\therefore \,\,\,|2\vec a \,\, + \,\,\vec b |\,\,\, $
$= \,\,\sqrt {|2\vec a \,\, + \,\,\vec b {|^2}\,} \,\, $
$= \,\,\sqrt {\left( {4{a^2}\,\, + \;\,{b^2}\,\, + \;\,4\,\,\left( {\vec a .\,\vec b } \right)} \right)} $
$ = \,\,\sqrt {\left( {16\,\, + \;\,9\,\, + \;\,0} \right)} \,\, $
$= \,\,5\,\,\,\,$
$\therefore \,\,|\vec p - \,\vec q |\,\, = \,\,|\vec p + \,\vec q |\,\,\,$
જ્યારે $\vec p \bot \,\vec q $ માત્ર ત્યારે જ શક્ય છે