IfA=[2 1 1 0] ,B= [1 -1 2 3] ,verify that : (A+B)2 not equalA to (A2+2

This question was asked in Example 22

IfA=[2 1 1 0] ,B= [1 -1 2 3] ,verify that : (A+B)2 not equalA to (A2+2AB+B2.