Question Number 81318 by ahmadshahhimat775@gmail.com last updated on 11/Feb/20
Commented by mr W last updated on 11/Feb/20
$$\mathrm{8}^{\mathrm{2}{n}} =\left(\mathrm{9}−\mathrm{1}\right)^{\mathrm{2}{n}} \equiv\mathrm{1}\:{mod}\:\mathrm{9} \\ $$