Match the following guess solutions yp for the method of und
Match the following guess solutions yp for the method of undetermined coefficients with the second-order nonhomogeneous linear equations below.
A. yp(x)=Ax2+Bx+C, B. yp(x)=Ae2x, C.yp(x)=Acos2x+Bsin2x,
D. yp(x)=(Ax+B)cos2x+(Cx+D)sin2x E. yp(x)=Axe2x, and F.yp(x)=e3x(Acos2x+Bsin2x)
1. d2ydx2+4y=xx220
2. d2ydx2+6dydx+8y=e2x
3. y+4y+20y=3sin2x
4. y2y15y=3xcos2x
Solution
1 ) Given that
(d2y/dx2) + 4y = x - x2 + 20
(d2y/dx2) + 4y = - x2 + x + 20
For a non homogeneous part - x2 + x + 20 , we assume the perticular solution is
yp(x) = Ax2 + Bx + C
2 ) Given that
d2y/dx2 + 6dy/dx + 8y = e2x
For a non homogeneous part e2x , we assume the perticular solution is
yp(x) = Ae2x
3 ) Given that
y + 4y + 20y = 3sin(2x)
For a non homogeneous part 3sin(2x) , we assume the perticular solution is
yp(x) = Acos(2x)+Bsin(2x)
4 ) Given that
y 2y 15y = 3xcos(2x)
For a non homogeneous part 3xcos(2x) , we assume the perticular solution is
yp(x) = (Ax+B)cos2x+(Cx+D)sin2x
