Question

Sa se determine suma primilor 8 termeni ai progresiei geometrice in care b1=2 si q=-1

Answer 1

S= b1 x q^n - 1/q - 1
S8= 2 x (-1)^8 - 1/ -1 -1
S8= 2 x 1 - 1/ -2
S8= 2 x 0/-2
S8= 2 x 0
S8= 0

Sau "metoda babeasca"

B1=2
B2=b1 x q^n+1 = 2 x -1 = -2
B3= 2 x 1= 2
B4= 2 x -1 = -2
Faci in continuare pana la B8 si apoi le aduni
2-2+2-2+2-2+2-2= 0