Question Number 9325 by tawakalitu last updated on 30/Nov/16
Answered by RasheedSoomro last updated on 30/Nov/16
$$\left(\mathrm{B}\right)\:\mathrm{12}\: \\ $$$$\mathrm{25}\equiv−\mathrm{1}\left(\mathrm{mod}\:\mathrm{13}\right) \\ $$$$\left(\mathrm{25}\right)^{\mathrm{15}} \equiv\left(−\mathrm{1}\right)^{\mathrm{15}} \left(\mathrm{mod}\:\mathrm{13}\right) \\ $$$$\left(\mathrm{25}\right)^{\mathrm{15}} \equiv−\mathrm{1}\left(\mathrm{mod}\:\mathrm{13}\right) \\ $$$$\left(\mathrm{25}\right)^{\mathrm{15}} \equiv−\mathrm{1}+\mathrm{13}\left(\mathrm{mod}\:\mathrm{13}\right) \\ $$$$\left(\mathrm{25}\right)^{\mathrm{15}} \equiv\mathrm{12}\left(\mathrm{mod}\:\mathrm{13}\right) \\ $$
Commented by tawakalitu last updated on 30/Nov/16
$$\mathrm{Thanks}\:\mathrm{so}\:\mathrm{much}\:\mathrm{sir}. \\ $$