Question

progresia geometrica clasa a 9-a  DACA AVEM B1=3 SI B5=$\frac{1}{27}$   AFLATI B2 B3 B4 SI S4  

Answer 1

In progresia geometrica notam cu a ratia progresiei, deci avem:

B1=3
B2=3*a
B3=3*$a^{2}$
B4=3*$a^{3}$
B5=3*$a^{4}$ = $\frac{1}{27}$

Din ultima relatie rezulta:

$a^{4}$ = $\frac{1}{81}$, adica

$a^{4}$ = $( \frac{1}{3} )^{4}$, deci

a=$\frac{1}{3}$ si avem:

B2=1
B3=$\frac{1}{3}$
B4=$\frac{1}{9}$