Question

(2+4+6...+100)-50.Imi puteti da pas cu pas va rog?

Answer 1

(2+4+6+..+100)-50 : 
(2+4+6+..+100) [ Dam factor comin pe 2]
2(1+2+3+...+50), apoi aplicam celebra suma a lui gauss : = 2 * [50*(50+1)]/2= 1275*2= 2550
Apoi scadem 50: 2550-50= 2500

Answer 2

In caz ca vrei sa arati ca e p.p :
[tex](2+4+6...+100)-50= \\ 2(1+2+3+...+50)-50= \\ 2*\frac{50(50+1)}{2}-50= \\ 50*51-50 = \\ 50(51-1)=50^2=p.p[/tex]