Plot x^2+y^2+xy+x+y=0 ?

[briglass]

Do you know how I could go about plotting this function?

x^2 + y^2 + xy + x + y = 0

Thanks,
Brian

 

[sboyce]

briglass, this looks suspiciously like a homework problem.

-Sam Boyce
Asst. Mechanical Engineer

http://www.AppleAid.com

 

[briglass]

It's not. It's for psych research. The actual equation is more complicated, but I just wanted to know how to plot non-seperable equations in general.

Anyway, I ended up using ezplot, and it works well.

-Brian

 

[sboyce]

Sorry then.

-Sam Boyce
Asst. Mechanical Engineer

http://www.AppleAid.com

 

[WCFoiles]

Why wouldn’t you just find a series of solutions and plot the points in the plane? If you want to plot line segments between points, I guess you could sort the data by x.

For this particular example I would be tempted to use an ad hoc method.

x^2+y^2+xy+x+y=0 can be re-written as

3/4x^2+1/2x+(y+1/2x)^2+(+y+1/2x)=0

Define u=y+1/2x then
3/4x^2+1/2 x +u^2+u=0

For an array of u values one gets x values by the quadratic formula (Possibly 2 solutions.). With the x values one gets the y values from the definition of u. Plot the points.


Regards,

Bill