### 5.58.8 Graph of a quadric: quadric

quadric takes as arguments the expression of a quadric with respect to x,y,z. You may also specify the variables as a vector (second argument) or as second, third and fourth arguments.
quadric draws this quadric.
Input:

quadric(7*x^2+4*y^2+4*z^2+4*x*y- 4*x*z-2*y*z-4*x+5*y+4*z-18)

Output:

Ellipsoid of center [0.407407407407,-0.962962962963,-0.537037037037]

See also reduced_quadric for the parametric equation of the quadric.