Question

Cum se calculeaza cu suma lui gauss 2+4+6+....100 sau 5+10+15......+55

Answer 1

2+4+6+....100= 2*1+2*2+2*3+.....2*50= 2*(1+2+3+...50)= 2*50*51 : 2=50*51=
= 2550


5+10+15......+55 = 5*1+5*2+5*3+....5*11= 5*(1+2+3+..11)= 5*11*12 : 2= 330

Pentru 1 + 2 + 3 +....+n
S= n * (n+1) / 2