y"=∑m(n-1)anx"2=∑n+2)n+1)an12x", nE 将y,y3,y"带入y"-xy-y=0, ∑(n+2)(n+1)am+2x"-x∑mnx”∑anx=0, n=0 n=0 ∑(m+2)n+1an2-(n+1ankx"≡0, n+2 n=0,1,2, n+22 1 ( 1) −  =  =  − n n y n n an x 将 y, y , y 带入 y − xy − y = 0, ( 2)( 1) , 0 2 n n  n n a n x  = = + + + 0, 0 −  =  = n n a n x 1 0 −  = −  n n x nan x n n  n n an x  = + + + 0 2 ( 2)( 1) [( 2)( 1) ( 1) ] 0, 0  + + 2 − +   = + n n n n a n n a n x , 2 2 + + = n a a n n n = 0,1,2, 