If A=1−121,B=a1b−1 and (A + B)2 = A2 + B2 + 2AB, then

Given, (A + B)2 = A2 + B2 + 2ABor (A + B) (A + B) = A2 + B2 + 2ABor A2 + AB + BA + B2 = A2 + B2 + 2AB or BA = ABor a1b−11−121=1−121a1b−1or a+2    −a+1b−2    −b−1=a−b1+12a+b2−1The corresponding elements of equal matrices are equal.a+2=a−b,−a+1=2⇒a=−1b−2=2a+b,−b−1=1⇒b=−2⇒ a=−1, b=−2