二阶矩阵的逆矩阵可用固定公式A=a bc dA^-1 = [1/(ad-bc)]*d -b-c a--主对角线换位置, 次对角线换符号1 -11 -3的逆 = -1/2 *-3 1-1 1=3/2 -1/21/2 -1/2
3/2 -1/21/2 -1/2
