Use an integrating factor to solve the following first order linear ODE. xy' + 2y = 3x, y(1) = 3 Find the end behavior of y as x rightarrow infinity.

Respuesta :

Answer:

Solution --> [tex] y(x) = x + \frac{2}{x^{2}} [/tex]

when x --> infinity the y goes to infinity too.

Step-by-step explanation:

We have the eq.

[tex] x y'+2 y = 3 x [/tex]

with y(1) = 3. So a reconfiguration o this last one equation can be like:

[tex] y' + \frac{2}{x} y = 3 [/tex]

so is of the form y'+p(x) y = f(x), where the integral factor is given by:

[tex] \mu = \exp[ \int p(x) dx] [/tex]

is,

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

Multiplying the whole equation with this integral factor we can write the expression:

[tex] \int \frac{d}{dx}[y x^{2}] dx = \int 3x^{2} dx [/tex]

and from this we obtain,

[tex] y x^{2} = x^{3} + c,[/tex]

So when y(x=1) = 3, c = 2 and the complete solution can be writen as:

[tex] y(x) = x - \frac{2}{x^{2}} [/tex].

And we can see that when x --> infinity the second term of the solution is practically zero and the first is infinity so y also goes to infinity when x does.