Question

Dau coroana
1. 2+4+3+...........+50=

2. 9+10+11+.........+30=

Answer 1

1) 2+4+3+5+6+....+50=
=1+2+3+4+5+.....+50-1=
=[(50x51)/2]-1=
=1275-1=
=1274
2)cuplezi termenii intre ei astfel inat sa ti fie mai usor sa aduni de exemplu pe 9,11,10 ii aduni si iti va da 20
=>9+10+11+12+18+13+17+14+16+15+25+19+20+21+22+28+23+27+24+26+29+30=
=30+30+30+30+30+60+50+50+50+40+29=
=150+100+150+29=
=429
:)