特征方程:r² + 2 = 0r = ±√2iy = C₁sin(√2x) + C₂cos(√2x)令特解p = Asinx + Bcosxp'' = - Asinx - Bcosx,代入方程得(- Asinx - Bcosx) + 2(Asinx + Bcosx) = sinx{ - A + 2A = 1 => A = 1{ - B + 2B = 0 => B = 0特解:p = sinx∴方程通解:y = C₁sin(√2x) + C₂cos(√2x) + sinx