] For A−1 must exist ad−bc≠0...... (i) and A=A−1⇒A2=I ∴a2+bc=d2+bc=1 and b(a+d)=c(a+d)=0 Case I : When a=d=0, then possible values of (b,c) are (1,1),(−1,1) and (1,−1) and (−1,1). Total four matrices are possible. Case II: When a=−d then (a,d) be (1,−1) or (−1,1). Then total possible values of (b,c) are (12+11)×2=46. ∴ Total possible matrices =46+4=50.