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Calculati 3a+4b+c daca a+b=10 si b+c=11

Răspuns :

a=10-b

c=11-b

rezultă

3a+4b+c= 3(10-b)+4b+(11-b)= 30-3b+4b+11-b=41

3a+4b+c=3a+3b+b+c=(3a+3b) + (b+c)=3(a+b) + (b+c)=3×10+11=30+11=41