a
આપણે એકજ સમતલના સદીશ માટેની શરત જાણીએ છીયે

\(\,\mathop a\limits^ \to  \,\, \times \,\,\left( {\,\mathop b\limits^ \to  \, \times \,\,\mathop c\limits^ \to  \,} \right)\,\, = \,\,\left| {\left. {\,\begin{array}{*{20}{c}}
{{a_x}}&{{a_y}}&{{a_z}}\\
{{b_x}}&{{b_y}}&{{b_z}}\\
{{c_x}}&{{c_y}}&{{c_z}}
\end{array}\,} \right|} \right.\,\, = \,\,0\)

\( \Rightarrow \,\,\left| {\left. {\,\begin{array}{*{20}{c}}
2&2&{ - 2}\\
5&y&1\\
{ - 1}&2&2
\end{array}\,} \right|} \right.\,\, = \,\,0\,\,\,\)

\( \Rightarrow \,\,2(2y - 2) - 2(11) - 2(10 + y) = 0\)

\( \Rightarrow \,\,4y - 4 - 22 - 20 - 2y = 0\,\,\)

\( \Rightarrow \,\,2y = 46\,\,\,\therefore \,\,y = 23\)