It is easy to check that for any value of c, the function y=x2+cx2 is solution of equation xy′+2y=4x2, (x>0). Find the value of c for which the solution satisfies the initial condition y(10)=2.

Respuesta :

Answer:

Therefore [tex]y=x^2+\frac{c}{x^2}[/tex] is a solution of [tex]xy'+2y=4x^2[/tex].

[tex]\therefore y=x^2-\frac{9800}{x^2}[/tex]

Step-by-step explanation:

The given differential equation is

[tex]xy'+2y=4x^2[/tex]

[tex]\Rightarrow y'+\frac{2y}{x}=4x[/tex]

Here [tex]P=\frac {2}{x}[/tex]  and Q= 4x

The integrating factor is [tex]=e^{\int p dx[/tex]

                                       [tex]=e^{\int \frac{2}{x} dx[/tex]

                                       [tex]=e^{2\ ln x}[/tex]

                                       [tex]= e^{lnx^2}[/tex]

                                       [tex]=x^2[/tex]

Multiplying the integrating factor both sides of the DE

[tex]x^2y'+x^2\frac{2y}{x}=4x.x^2[/tex]

[tex]\Rightarrow x^2 \frac{dy}{dx}+2yx=4x^3[/tex]

[tex]\Rightarrow x^2dy+2yxdx=4x^3dx[/tex]

Integrating both sides

[tex]\int x^2dy+\int 2yxdx=\int 4x^3dx[/tex]

[tex]\Rightarrow x^2y= \frac{4x^4}{4}+c[/tex]          [ c is an arbitrary constant]

[tex]\Rightarrow x^2y =x^4+c[/tex]    

[tex]\Rightarrow y=x^2+\frac{c}{x^2}[/tex]             [ dividing by x²]

Therefore [tex]y=x^2+\frac{c}{x^2}[/tex] is a solution of [tex]xy'+2y=4x^2[/tex].

The initial condition is y(10)=2

Putting x=10 and y=2

[tex]\therefore 2=10^2+\frac{c}{10^2}[/tex]

[tex]\Rightarrow 200= 10000+c[/tex]   [ multiply by 100]

[tex]\Rightarrow c=200-10000[/tex]

[tex]\Rightarrow c=-9800[/tex]

Putting the value of c in the solution we get,

[tex]\therefore y=x^2-\frac{9800}{x^2}[/tex]

Yes, the function [tex]y=x^{2} +\frac{c}{x^{2} }[/tex] is solution of given differential equation.

The value of c is -9,800.

Differential equation:

The given differential equation is,

                 [tex]xy'+2y=4x^{2} \\\\y'+\frac{2}{x}y=4x[/tex]

Compare above equation with [tex]y'+Py=Q[/tex]

We get, [tex]P=\frac{2}{x} ,Q=4x[/tex]

Now we have to find integrating factor,

                            [tex]=e^{\int\limits {\frac{2}{x} } \, dx } \\\\=e^{2ln(x)}=x^{2}[/tex]

So that,

                  [tex]y*x^{2} =\int\limits {4x^{3} } \, dx \\\\y*x^{2} =4*\frac{x^{4} }{4} +c\\\\y=x^{2} +\frac{c}{x^{2} }[/tex]

the initial condition y(10)=2,

            [tex]2=100+\frac{c}{100} \\\\c=-9800[/tex]

Hence, the value of c is -9,800.

Learn more about the differential equation here:

https://brainly.com/question/1164377

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