1.△yt=y(t+1)-y(t)=(t+1)³-t³△²yt=y(t+2)-2y(t+1)+yt=(t+2)³-2(t+1)³+t³2.一阶线性非齐次差分齐次特征方程：λ-1=0则λ=1齐次通解为：C(1)^t=Cf(t)型为ρ^t×Pm(t),ρ=1为特征方程...