Question

6+11+16+21+...+106=? va rog am lipsit cand s-a explicat so like now im a lost case Daca ati putea si sa o explicati tho

Answer 1

 

$\displaystyle\bf\\Pasul~1\!\! :~Calculam~numarul~de~termeni~(n).\\\\n=\frac{106-6}{5}+1=\frac{100}{5}+1=20+1=21~de~termeni.\\\\unde~5~este~pasul~(diferenta~dintre~2~termeni~consecutivi.)\\\\Pasul~2\!\! :~~Folosim~formula~lui~Gauss~pentru~suma.\\\\6+11+16+21+...+106=\frac{n(106+6)}{2}=\frac{21\times112}{2}=21\times56=1176\\\\\boxed{\bf6+11+16+21+...+106=1176}$