Ex 3.4, 4 - Chapter 3 Class 12 Matrices (Term 1)

Transcript

Ex3.4, 4 Find the inverse of each of the matrices, if it exists. [■8(2&[email protected]&7)] Let A = [■8(2&[email protected]&7)] We know that A = IA [■8(2&[email protected]&7)] = [■8(1&[email protected]&1)] A R1→1/2R1 [■8(𝟐/𝟐&3/[email protected]&7)] = [■8(1/2&0/[email protected]&1)] A [■8(𝟏&3/[email protected]" " &7" " )] = [■8(1/2&0[email protected]&1)] A R2 →R2 – 5R1 [■8(1&3/[email protected]𝟓−𝟓" " &7−5 (3/2)" " )] = [■8(1/2&[email protected]−5/2&1−5(0))] A [■8(1&3/[email protected]𝟎" " &−1/2)] = [■8(1/2&[email protected](−5)/2&1)] A R2 → -2R1 [■8(1&3/[email protected]−2(0)" " &−𝟐((−𝟏)/𝟐) )] = [■8(1/2&[email protected]−2((−5)/2)&−2(1))] A [■8(1&3/[email protected]" " &𝟏)] = [■8(1/2&[email protected]&−2)] A R1 →R1 – 3/2 R2 [■8(1−0(3/2)&𝟑/𝟐−𝟑/𝟐(𝟏)@0" " &1)] = [■8(1/2−3/2(5)&0−3/2(−2)@5&−2)] A [■8(1&𝟎@0" " &1)] = [■8(−7&[email protected]&−2)] A This is similar to I = A-1A Thus, A-1 = [■8(−7&[email protected]&−2" " )]