Question

Sa se calculeze sumele :
a)Sn=1+3+5+7+...+(2n+1)
b)Sn=3+7+11+...+(4n-1)
c)Sn=2x+(2x-3)+(2x-6)+...+(2x-3n+3)
Dau coroana!

Answer 1

Gauss a descoperit aceste sume,implicit si formulele.Folosesti formula lui Sn=[(primul termen+ultimul termen)*nr de termini]:2

[(2n+2)*(n+1)]/2=(n+1)patrat

b)(3+4n-1)*2n/2=(4n+2)*n