求下列常系数线性非齐次方程的通解或特解:
(1)y"+2y'+y=xe-x;
(2)y"-4y'+3y=1-e3x;
(3)y"-2y'-3y=6+e-x,y(0)=0,y'(0)=0;
(4)y"-4y=xex,y(0)=1,y'(0)=2;
(5)y"+y'-2y=7cosx-sinx,y(0)=0,y'(0)=1。
求下列线性差分方程的通解或特解:
(1)yn+2+3yn+1=0;
(2)yn+1-2yn=2n2-1;
(3)yn+1-yn=n+3;
(4)yn+1-3yn=3n;
(5)yn+1-2yn=-cos2n;
(6)yn+1+2yn=2n-1+en;
(7)yn+1+2yn=3·2n,y0=0。
设y1(x)、y2(x)是二阶齐次线性方程y''+p(x)y'+q(x)y=0的两个解,令证明: