Răspunsuri

2014-10-13T15:58:16+03:00
Sn=(a₁+an)n/2
s₅₀=(2+50)x49/2=52x49/2=26x49=1274

S₇₀(15+70)56/2=85x56/2=85x28=2380

S₄₀₀=(317+400)84/2=717x84/2=717x42=30114