Identify a basis for the following subspace: W equals open curly brackets open square brackets table row cell negative a end cell cell a minus b end cell row cell 2 b end cell cell 3 a end cell end table close square brackets element of straight real numbers subscript 2 x 2 end subscript vertical line a comma b space element of straight real numbers close curly brackets space i s space a space s u b s e t space o f space straight real numbers subscript 2 x 2 end subscript