Question

5+10+15+….+2275 va dau coroana

Answer 1

Răspuns:

2.305

Explicație pas cu pas:

15+10+15+2.275=2.305

Answer 2

avem o progresie aritmetică

$\bf a_1=5,\ \ r=5\\ \\ a_n=a_1+(n-1)r=5+(n-1)\cdot5=5(1+n-1)=5n=2275 \Rightarrow \\ \\ \Rightarrow n=455\\ \\ S=\dfrac{(5+2275)\cdot455}{2}=1140\cdot455$