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determinati a+b+c,daca: a+b=1331, b+c= 1624, a+c= 1385

Răspuns :

a+b=1331
b+c=1624
a+c=1385
-------------- le adunam
⇒ 2a +2b+2c = 1331+1624+1385
⇒2(a+b+c) = 4340
⇒a+b+c = 4340 :2
⇒a+b+c = 2170
a+b+c=(a+b+b+c+a+c)/2
a+b+c=(2a+2b+2c)/2
a+a+b+b+c+c=a+b  +b+c   +b+c=1331+1624+1385=   4340