Proof of Solutions for y' = xg(x,y) Equation

  • Thread starter Thread starter Fibonacci88
  • Start date Start date
  • Tags Tags
    Existence Ode
Fibonacci88
Messages
2
Reaction score
0
Given the equation y'= xg(x,y) , suppose that g and (partial) dg/dy are defined and continuous for all (x,y). Show the following:

1) y(x)=0 is a solution

2)if y=y(x), x in (a,b) is a solution and if y(x0)>0, x0 in (a,b), then y(x)>0 for all x in (a,b)

Please i need your help.
 
Physics news on Phys.org
Fibonacci88 said:
Given the equation y'= xg(x,y) , suppose that g and (partial) dg/dy are defined and continuous for all (x,y). Show the following:

1) y(x)=0 is a solution
You can't- it's not true. For example, supose g(x,y)= 1 so the equation is y'= x. Then y(x)= (1/2)x^2+ C. y(x)= 0 is not a solution since then y'= 0 and so y'= 0\ne x. there may be some other condition that you have left out.

2)if y=y(x), x in (a,b) is a solution and if y(x0)>0, x0 in (a,b), then y(x)>0 for all x in (a,b)

Please i need your help.
 
sorry for mistake. I am sending the correct version of the problem now.

i need answer for (ii) and (iii)
 

Attachments

  • odee.jpg
    odee.jpg
    31.4 KB · Views: 360
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
Back
Top