Question

sa se demonstreze inegalitatea 1+2+...+60 mai mic decat 9(1+2+...+20

Answer 1

1+2+...60=60x61/2 =3660/2=1830
9(1+2+...+20)=9(20x21/2)=9x420/2=9x210=1890
1830 mai mic decat 1890
/-inseamna impartire

Answer 2

1+2+...+60=60·61:2=30·61=1830
9(1+2+...+20)=9·20·21:2=90·21=1890
cum 1830 este mai mic decat 1890 si prima egaliate  e mai mica decat a doua