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,
F.yp(x)=e3x(Acos2x+Bsin2x)
1. d2ydx2+4y=x−x220
2. d2ydx2+6dydx+8y=e2x
3. y′′+4y′+20y=−3sin2x
4. y′′−2y′−15y=3xcos2x

Respuesta :

Answer and Step-by-step explanation:

1. Data provided

[tex]\frac{d^2y}{dx^2} + 4y = x - x^2 + 20\\\\ \frac{d^2y}{dx^2} + 4y = - x^2 + x + 20[/tex]

Now as a non homogeneous part which is

[tex]- x^2 + x + 20[/tex] let us assume the computation is

[tex]y_p(x) = Ax^2 + Bx + C[/tex]

2. Data provided

[tex]\frac{ d^2y}{dx^2} + \frac{6dy}{dx} + 8y = e^{2x}[/tex]

As a non homogeneous part is [tex]e^2x[/tex] , let us assume the computation is

[tex]y_p(x) = Ae^{2x}[/tex]

3. Data provided

[tex]y'' + 4y' + 20y = -3sin2x[/tex]

As a non homogeneous part −3sin(2x), let us assume the computation is

[tex]y_p(x) = Acos(2x) + Bsin(2x)[/tex]

4. Data provided

[tex]y'' - 2y' - 15y = 3xcos(2x)[/tex]

As a non homogeneous part  3xcos(2x), let us assume the computation is

[tex]y_p(x) = (Ax+B)cos2x+(Cx+D)sin2x[/tex]