The comments are correct. It is more of a math problem. You draw a line 2x - y = 0
and translate it for any z
value to create a plane.
[x, y] = meshgrid(-5:0.5:5);
Zv = @(x,y) 1 - x - y;
mesh(x,y,Zv(x,y));
hold on
[x, z] = meshgrid(-5:0.5:5);
Yv = @(x) 2*x;
mesh(x,Yv(x),z);
hold off