(後只人季 记x的系数作A 112a13 十 十 1 22 23 12233 22331 2132 32 33 112332 202133 1322231 1 2 3 3 2 1 2 2 1 3 3 1 3 2 2 3 1, 1 1 2 2 3 3 1 2 2 3 3 1 1 3 2 1 3 2 a a a a a a a a a a a a a a a a a a − − − = + + 3 1 3 2 3 3 2 1 2 2 2 3 1 1 1 2 1 3 a a a a a a a a a A = (1.8) 记x1 的系数作A