# Differential Equations (first order)

• Dec 8th 2010, 12:15 PM
cassius
Differential Equations (first order)
I need to solve:

1) (2x-y+5)*dy/dx + x -2y +3=0

here, I made the derivative the subject then substituted to get rid of the constants... in the end I got
(x+y+2)^3 = (y-x-8/3)/(k^2) where lnk= C (constant of integration)
Is this right? a friend got (x-y+8/3)*k^2 on the right-hand side

any help is much appreciated
• Dec 8th 2010, 04:53 PM
ark600
I dont know what you mean- you might be making this more complicated than necessary.
If you make the substition z=-x, then you have a differential equation of the form
A(z,y) + B(z,y)dz/dy = 0
where \$\displaystyle A_y = B_z\$ [not my favoured notation but Im not familiar with the BBcodething for partial derivatives: anyway it equals -2 in this example]
this is a standard equation with solvable method described in good textbooks I guess .

[ Simpler if you are not familiar with the above: y=-x+C is a solution by inspection, and you can work out C]