(7p+2q)^2+(7p-2q)^2=
=49*q^2+28*p*q+49*p^2+4*q^2-28*p*q+49*p^2=
8*q^2+98*p^2
(3d+5c)^2-(3d-5c)^2=
=9*d^2+30*c*d+25*c^2-9*d^2+30*c*d-25*c^2=
=60*c*d
