2 2 6*c - 6*d
6*c^2 - 6*d^2
1*(c + d)*(c - d)
(1*(c + d))*(c - d)
/ 2 2\ 6*\c - d /
6*(c^2 - d^2)
6*(c + d)*(c - d)
6.0*c^2 - 6.0*d^2