What is 3−1+3−2 (mod 25)? Express your answer as an integer from 0-24 inclusive.
What is 3−1+3−2(mod25)?
Express your answer as an integer from 0-24 inclusive.
My attempt:
3−1+3−2(mod25)≡3−1+3−13−1(mod25)≡3−1(1+3−1)(mod25)
3−1(mod25)= ?
3−1(mod25)≡13(mod25)≡3ϕ(25)−1(mod25)|ϕ(25)=20≡320−1(mod25)≡319(mod25)≡33∗6+1(mod25)≡33∗6∗3(mod25)≡(33)6∗3(mod25)|33=27≡2(mod25)≡26∗3(mod25)≡192(mod25)3−1(mod25)≡17(mod25)
3−1+3−2(mod25)≡3−1(1+3−1)(mod25)|3−1(mod25)≡17(mod25)≡17(1+17)(mod25)≡17∗18(mod25)≡306(mod25)3−1+3−2(mod25)≡6(mod25)