Question

1+2+3+...+30 ; 2+3+4+...+30; 9+10+11+...+30​

Answer 1

Răspuns:

Explicație pas cu pas:

$\bf a)~~1 + 2 + 3 +....+ 30 =$

$\bf 30\cdot(1+ 30):2 =$

$\bf 30\cdot31:2 =$

$\bf 15\cdot31=$

$\green{\bf \underline{~465~}}$

$\bf b)~~2 + 3 + 4+...+30=$

$\bf (2 +30)\cdot[(30-2):1+1]:2=$

$\bf 32\cdot(28:1+1):2=$

$\bf 32\cdot 29:2=$

$\bf 16\cdot 29=$

$\purple{\underline{\bf~ 464~}}$

$\bf c)~~9 + 10 + 11 +...+30 =$

$\bf (9 + 30)\cdot[(30-9):1+1]:2 =$

$\bf 39\cdot(21:1+1):2 =$

$\bf 39\cdot 22:2 =$

$\bf 39\cdot 11=$

$\red{\bf \underline{~429~}}$

Mai multe detalii despre astfel de exerciții ai aici: https://brainly.ro/tema/7277903

https://brainly.ro/tema/7168515

Baftă multă !