Formula termenului general an=ao*q^(n-1)=q^(n-!)
an+1=ao*q^(n+1-1)=q^(n)
an-1=ao*q^(n-1-1)=q^(n-2)
InlocuieSTI acESTI TERMeNI in formula data
q^n=3*q^(n-1)-2*q^(n-2)
Imparti ecuatia prin q^(n-2)
q^(n-(n-2))=3*q^[n-1-(n-2)]-2
q^2=3q-2
q^2-3q+2=0
q1=1 nu se accepta
q2=2 se accepta
Aplici formula sumei unei PG
Sn=a0*[(q^(n+1)-1]/(q-1) unde ao=1 si q=2
Sn={2^{n+1)-1)/(2-1)=2^(n+1)
Intrebari?
