### 15.6.8 Graph of a quadric

The quadric command draws a quadric.

- quadric takes one mandatory argument and one optional argument:
  - q, the expression of a quadric.
  - Optionally, vars, a list of three variable names (by default, [x,y,z]). These names can also be given a separate arguments.
- quadric(q⟨,vars⟩) draws this quadric.

#### Example

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)

Ellipsoid with center [0.407407407407,−0.962962962963,−0.537037037037]

See also the next section for the parametric equation of the quadric.