例y(n)-3y(n-1)+3y(n-2)-y(n-3)=x(n) 三重根 y(n)=(C1n2+C2n+C3)(+1) 齐次解 x(0)=1,x(-1)=0,x(-2)=0, 确定初始 条件 h(0)=1,h(-1)=0,h(-2)=0, h(m)=-(n2+3n+2)(n)5 例 y(n) −3y(n −1) + 3y(n − 2) − y(n −3) = x(n) 1=  三重根 n y(n) (C n C n C )( 1) 2 3 2 = 1 + + + 齐次解 x(0) =1, x(−1) = 0, x(−2) = 0,  h(0) =1, h(−1) = 0, h(−2) = 0,  确定初始 条件 1 2 3 2 1 C1 = C2 = C3 = ( 3 2) ( ) 2 1 ( ) 2 h n = n + n + u n