Răspuns:
Explicație pas cu pas:
[tex]\bf a)~~1 + 2 + 3 +....+ 30 =[/tex]
[tex]\bf 30\cdot(1+ 30):2 =[/tex]
[tex]\bf 30\cdot31:2 =[/tex]
[tex]\bf 15\cdot31=[/tex]
[tex]\green{\bf \underline{~456~}}[/tex]
[tex]\bf b)~~2 + 3 + 4+...+30=[/tex]
[tex]\bf (2 +30)\cdot[(30-2):1+1]:2=[/tex]
[tex]\bf 32\cdot(28:1+1):2=[/tex]
[tex]\bf 32\cdot 29:2=[/tex]
[tex]\bf 16\cdot 29=[/tex]
[tex]\purple{\underline{\bf~ 464~}}[/tex]
[tex]\bf c)~~9 + 10 + 11 +...+30 =[/tex]
[tex]\bf (9 + 30)\cdot[(30-9):1+1]:2 =[/tex]
[tex]\bf 39\cdot(21:1+1):2 =[/tex]
[tex]\bf 39\cdot 22:2 =[/tex]
[tex]\bf 39\cdot 11=[/tex]
[tex]\red{\bf \underline{~429~}}[/tex]
Mai multe detalii despre astfel de exercitii ai aici: https://brainly.ro/tema/7277903
https://brainly.ro/tema/7168515
Bafta multa !
