code: public Vector3D mult(Vector3D source) {
          Vector3D result = new Vector3D();
          result.setX(m00 * source.getX() + m01 * source.getY() + m02);
          result.setY(m10 * source.getX() + m11 * source.getY() + m12);
          return result;
      }
docs: Multiply the x and y coordinates of a Vertex against this matrix.