Question

Fie progresia geometrica in care b1=3 si b2=6. Sa se calculeze suma primilor 6 termeni ai progresiei.

Answer 1

aflam ratia q=$\frac{b_{n+1} }{ b_{n} }= \frac{b_{2} }{b_{1} } = \frac{6}{3} =2$

S₆=$\frac{b_{1}(q^{6}-1) }{q-1} = \frac{3(2^{6}-1) }{2-1} = \frac{3(64-1)}{1}=3*63=189$