Răspuns:
[tex]b_{5} = 7[/tex]
Explicație pas cu pas:
q=2
[tex]b_{7} = 28\\b_{5} = ?[/tex]
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[tex]b_{n} =b_{n-1}*q[/tex]
[tex]b_{7} = b_{7-1} * q[/tex]
[tex]=> 28 = b_{6} * 2[/tex]
[tex]b_{6} = \frac{28}{2} = 14[/tex]
[tex]b_{6} = b_{6-1} * q\\=> 14 = b_{5} *q\\=> b_{5} = \frac{14}{2} =7[/tex]
