Pls solve it!!!!:


$\mathrm{B}-7. \mathrm{Show} \mathrm{that} \left|\begin{array}{ccc}{\mathrm{a}}_1{\mathrm{I}}_1+{\mathrm{b}}_1{\mathrm{m}}_1& {\mathrm{a}}_1{\mathrm{I}}_2+{\mathrm{b}}_1{\mathrm{m}}_2& {\mathrm{a}}_1{\mathrm{I}}_3+{\mathrm{b}}_1{\mathrm{m}}_3\\ {\mathrm{a}}_2{\mathrm{I}}_1+{\mathrm{b}}_2{\mathrm{m}}_1& {\mathrm{a}}_2{\mathrm{I}}_2+{\mathrm{b}}_2{\mathrm{m}}_2& {\mathrm{a}}_2{\mathrm{I}}_3+{\mathrm{b}}_2{\mathrm{m}}_3\\ {\mathrm{a}}_3{\mathrm{I}}_1+{\mathrm{b}}_3{\mathrm{m}}_1& {\mathrm{a}}_3{\mathrm{I}}_2+{\mathrm{b}}_3{\mathrm{m}}_2& {\mathrm{a}}_3{\mathrm{I}}_3+{\mathrm{b}}_3{\mathrm{m}}_3\end{array}\right|=0$