Question

2+4+6+..100 sau 3+5+7+...+101 cum se procedeaza?

Answer 1

in prima variante se aduna doar numerele pare(2,4,6,8,10,12,14...etc) , iar in a doua varianta se aduna doar numerele impare(1,3,5,7,9,11..etc)

Answer 2

2+4+6+..100=2(1+2+3+...+50)=2((1+50)×50:2)=2(51×25)=2×1275=2550
3+5+7+...+101=2+3+4+5+...+100+101-(2+4+6+...+100)=..se procedeaza ca la prima, folosind formula (primul numar +ultimul)×numarul dee termeni supra 2