14) Calculati:
a) 2(3a+9b-7c)-3(4a+5b+9c)-5(a+2b-8c)


Răspuns :

2(3a+9b-7c)-3(4a+5b+9c)-5(a+2b-8c)
= 6a+18b-14c-12a-15b-27c-5a-10b+40c
= -11a  -7b -c