(a) Show that every member of the family of functions y = (6 ln(x) + C)/x , x > 0, is a solution of the differential equation x2y' + xy = 6. (Simplify as much as possible.)

Respuesta :

Answer:

Therefore , every element of the function [tex]y =\frac{6 \ ln (x)+c}{x}[/tex] is a solution of the DE  [tex]x^2y'+xy=6[/tex].

Step-by-step explanation:

Given differential equation is

[tex]x^2y'+xy=6[/tex]

[tex]\Rightarrow y'+\frac{xy}{x^2}=\frac{6}{x^2}[/tex] [ divided by x²]

[tex]\Rightarrow y'+\frac{y}{x}=\frac{6}{x^2}[/tex]

Here [tex]P= \frac{1}{x}[/tex] and [tex]Q=\frac{6}{x^2}[/tex]

The integrating factor is =  [tex]e^{\int pdx}[/tex]

                                        [tex]=e^{\int \frac{1}{x}dx[/tex]

                                        [tex]=e^{ln x}[/tex]

                                        = x

Multiplying the integrating factor both sides of the ODE

[tex]x y'+x.\frac{y}{x}=x. \frac{6}{x^2}[/tex]

[tex]\Rightarrow xy'+y=\frac{6}{x}[/tex]

[tex]\Rightarrow x\frac{dy}{dx}+y=\frac{6}{x}[/tex]    [ [tex]\because y'=\frac{dy}{dx}[/tex] ]

[tex]\Rightarrow xdy+ydx=\frac{6}{x}dx[/tex]

Integrating both sides

[tex]\int xdy+\int ydx=\int\frac{6}{x}dx[/tex]

[tex]\Rightarrow xy= 6\ ln(x)+c[/tex]   [ c is an arbitrary constant]

[tex]\therefore y =\frac{6 \ ln (x)+c}{x}[/tex]         for x>0

Therefore , every element of the function [tex]y =\frac{6 \ ln (x)+c}{x}[/tex] is a solution of the DE  [tex]x^2y'+xy=6[/tex].