(3A)^(-1) = (1/3) A^(-1)A* = |A|A^(-1) = (1/2) A^(-1)所以 |（3A）^-1 - 2A^*|= | (1/3) A^(-1) - (1/2) A^(-1) |= | (-2/3) A^(-1) | = (-2/3)^3 | A^(-1) | = (-2/3)^3 * 2 = - 16/27
