In general, the structure of the equation to be solved is an n-order polynomial multiplied by an exponential function on the right side of the equal sign. If there is only an exponential function, we think that the polynomial is 1, that is, a polynomial of order 0.

So let the special solution be Pm(t)? q^t？ T k (three parts)

(1) PM (t) is a polynomial general form consistent with the polynomial of t on the right side of the original equation (second order at 2+Bt+C, first order At+B, zero order a, and so on);

② q^t is an exponential function on the right of the original equal sign;

③ T k k takes 0 or 1. When the bottom q of the original exponential function = the solution of the characteristic equation (λ), take 1, otherwise take 0. The essence is that if it is equal, multiply it by a t in the special solution;

Then bring the special solution into the original formula, and the corresponding items are equal after finishing, and solve the undetermined coefficients, that is, A, B and C you set, and then bring back the set special solution.