二、解的敛散性 1.由达氏判 R=lim k→∞ k+1 k+2 lim (k+2)(k+1) (+1)-k(k+1 x<1收敛 x>1发散 ④)当 x=1收敛?发散?二、解的敛散性 1.由达氏判 1 2 lim lim k k k k k k a c R ®¥ a c ®¥ + + = = ( ) ( )( ) ( ) ( ) 3 2 1 lim 1 k 1 - 1 k k ®¥ l l k k + + = = + + ∴y(x)当 x < 1 收敛 x > 1 发散 x = 1 收敛 发? 散?