Question

E(x)=2x-1
Aratati ca E(1) + E(2) + E(3) + ... + E(49) = patrat perfect.

Answer 1

E(1) =2*1-1=1
E(2) =2*2-1=3
E(3)=2*3-1=5
.........................
E(48)=2*48-1=95
E(49)=49*2-1=97
E(1) + E(2) + E(3) + ... + E(49)=1+3+5+.......=95+97= 98+98+...98
catide 98 avem? avem de la 1 la 49, ecxact 49de numere,  49/2  perechi
 asadar

E(1) + E(2) + E(3) + ... + E(49)=98*49/2=49*49=49², patrat perfect C.C.T.D.