👤

S=7^100+7^103+7^106+...+7^301.
Calculati S.


Răspuns :

S=7^100(1 +7³+7^6+....7^201)
notand 7^3=u

S= 7^100(1+u+u²+....+u^67)=7^100(u^68-1)/(u-1)
adica
S=7^100(7^204-1)/(7^3-1)

S= [7^100(7^204-1)]/342