分为齐次解和特解y''-3y'+2y = 0特征方程：t^2 - 3t + 2 = 0==> t = 1 or 2==> y = c1'e^x + c2'e^(2x)Y＝x(ax＋b)e^-xY'＝[－ax^2＋（2a－b)x＋b]e^-x Y''＝[ax^2－（4a－b）x＋2a－2b]e^-x 带入方程,得：[ax^2－（...