Question

Determinati b1 (primul termen) si q (ratia) daca$\left \{ {{b1-b5=15} \atop {b1-b3=12}} \right.$

Answer 1

b1 - b1q^4 =15
b1 - b1q^2 = 12
b1(1-q^2)(1+q^2)=15
12(1+q^2)=15
1+q*2=15/12
q^2=3/12
q^2=1/4, q=1/2