Question

Puteți sa mă ajutați ca am nevoie urgent va rog frumos!!!
1) 1+4+...+52

2) 2+7+12+...+57

3) 3+5!7+...+2015

Answer 1

1) (3*0+1) + (3*1+1) +...+(3*17+1)= 3*(0+1+2+...+17) + 1*18=
=3*17*18:2+18=51*9+18= 459+18=477

2) (5*0+2) +(5*1+2) + ...(5*11+2)= 5*(0+1+2+...+11) + 2*12=
5*11*12:2+24=55*6+24=330+24=354

3)(2*0+1) + (2*1+1)+(2*2+1)+....+(2*1007+1)=
=2*(0+1+2+...+1007) + 1*1008=
2*1007*1008:2+1008=
1007*1008+1008=
1008* (1007+1)=
1008*1008=
1008²=1016064