please help me plot this two odefunction yy'+36x=0 and xy'=y^2+y

emergency question

Answer 1

[Carlos Guerrero García]

Your goal is not clear for me, but I try to help. Because we can separate the varaibles in both odes, the general solution of the 1st ode is y^2+(6x)^2=k being k any constant, and the general solution of the 2nd ode is y/(x(y+1))=c, being c any constant. So, the following lines makes a sketch of these families:

[x,y]=meshgrid(-5:0.01:5); % The sketching window
subplot(1,2,1); % using first half of the figure...
contour(x,y,y.^2+36*x.^2,[0:40:400],'r'); % ...to draw the general solution of the 1st ode...
subplot(1,2,2); % ...and using the second half...
contour(x,y,y./(x.*(y+1)),[0:1/20:1],'b'); %...to draw the general solution of the 2nd ode

Is this, the figure you're looking for ???

[John D'Errico]

Please don't do student homework assignments for them, when posted with no effort made. It does not help the student. It does not help the site, because it convinces this student, and others who will follow, that you and others will do obvious homework assignments for students.

If you wanted to help the student, you might have pointed the person in the right direction. Suggest they look at their class notes about how to solve separable ODEs, but stop there.

[Carlos Guerrero García]

Thanks for the suggestion, John!!!

I'm newbie in the community and I'll take your comment in consideration