Question

Sa se gaseasca primul termen si ratia unei progresii geometrice daca
a6=25 si a8=9

Answer 1

a8=a6*q^2
q^2=a8/a6
q^2=9/25
=>q=3/5
    q=-3/5
a6=a1*q^5
a1=a6/q^5
a1=25/q^5 (=> calcule)
=>a1=5^7/3^5
    a1=-5^7/3^5

Answer 2

a₈=a₆×q²
q²=a₈:a₆
q²=9:25
$q= \sqrt{ \frac{9}{25} }= \frac{3}{5}$
a₆=a₁×q$^{5}$
a₁=a₆:q$^{5}$
a₁=25:(3/5)⁵