Question

1+4+9.......+301
2+5+8+....+599

Answer 1

1 + 5 + 9 + ...... + 301 = 11 476

→ stabilesc cati termeni are suma cu ratia = 4

( 301 - 1 ) : 4 + 1 = 300: 4 + 1 = 75 + 1 = 76

→ aplic formula sumei lui Gauss

= 76 × ( 1 + 301 ) : 2 =

= 38 × 302 =

= 11 476

________________________

2 + 5 + 8 + ........ + 599 =60 100

( 599 - 2 ) : 3 + 1 = 597 : 3 + 1 = 199 + 1 = 200 termeni

= 200 × ( 2 + 599 ) : 2 =

= 100 × 601 =

= 60 100