@acer Thank you very much, it works!

@Carl Love 

I'm sorry for the typo, the function should be 2x^2 + 3y^2 - x*y - 4, and now it seems parameterization is what I need to do.
Your answer is very helpful, thanks again!

Hyan
 

@Kitonum  Thank you very much!

@Carl Love 
Hello Carl, thank you for replying.
I was just asked to draw two curves by using the spacecurve command. The function provided is f(x,y)=2*x^2+3^2-x*y-4, and the curves required are f(x,1) and f(1,y), but it didn't mention anything about intersection. I know spacecurve is for vector sketching, but f(x,1) and f(1,y) should be polynomials right? so I am wondering if I miss some point here.

@acer @Kitonum  @Markiyan Hirnyk 

Thank you guys, your solutions all work well, I appreciate your help :)