(a-2b+c+3d)(a+2b-c+3d)=
4个回答

(a-2b+c+3d)(a+2b-c+3d)

=[(a+3d)+(c-2b)][(a+3d)-(c-2b)]

=(a+3d)²-(c-2b)²

=a²+6ad+9d²-c²+4bc-4b²