Question

fie expresia:2+6+10+....+2x=338​

Answer 1

Explicație pas cu pas:

2+6+10+...+2x=338=>

2(1+3+5+...+x)=338=>

1+3+5+...+x=169

Observam ca avem o suma Gauss de termeni consecutivi impari (1+3+5+..+x) deci suma va fi =k² unde 2k-1=x

2k-1=x=>2k=x+1=>k=(x+1)/2

k²=169=>k=13=>

(x+1)/2=13=>x+1=26=>x=25