3919.sagews

(x, y, z)

var('x y z')
para1=plot3d(x^2+2*x+y^2,(x, -1.5,1.5), (y, -1.5,1.5), color='blue', opacity=.3)
plane1=plot3d(2*x+1,(x, -1.5,1.5), (y, -1.5,1.5), color='red', opacity=.3)
show(para1+plane1+text3d("x",(0,-1.5,-2))+text3d("y",(1.5,0,-2)), mesh=True)