Răspuns:
[tex]b4=?[/tex]
[tex]b3=2[/tex]
[tex]b5=8[/tex]
Metoda 1)
[tex]b4=\sqrt{b3*b5} =\sqrt{2*8}=\sqrt{16}=>b4=4[/tex]
Metoda 2)
[tex]b3=b1*q^2=2\\b5=b1*q^4=8[/tex]
[tex]=>\frac{b3}{b5}=\frac{b1*q^2}{b1*q^4} =\frac{2}{8} =>\frac{1}{q^2}=\frac{1}{4} =>q^2=4=>q=2[/tex]
[tex]b4=b3*q = 2*2=> b4= 4[/tex]
