(3a+4b-2c)+(-5a-6b+4c)-(4a-7b-5c)

Răspuns :

(3a+4b-2c)+(-5a-6b+4c)-(4a-7b-5c) =
=
3a+4b-2c-5a-6b+4c-4a+7b+5c=
 
=-6a+5b+7c