Let A=⎣⎡12−225−437−5⎦⎤
Consider A=IA ∴⎣⎡12−225−437−5⎦⎤=⎣⎡100010001⎦⎤A
Applying R2→R2−2R1,R3→R3+2R1, we get ⎣⎡100210311⎦⎤=⎣⎡1−22010001⎦⎤A
Applying R1→R1−3R3,R2→R2−R3, we get ⎣⎡100210001⎦⎤=⎣⎡3−42−210−1−11⎦⎤A
Applying R1→R1−2R2, we get ⎣⎡100010001⎦⎤=⎣⎡3−42−210−1−11⎦⎤A ∴A−1=⎣⎡3−42−210−1−11⎦⎤