Question

Calculati 1+6+6^2+....+6^2018. Am nevoie urgent de ajutor pana la ora 19:30 cel mult!!!!!! Dau coroana

Answer 1

$S=1+6+6^2+... +6^{2018}|*6\\6S=6+6^2+6^3+6^4+...+6^{2019}\\6S-S=6^{2019}-1\\5S=6^{2019}-1\\\\S=\frac{6^{2019}-1}{5}$