Find the inverse of 7 modulo 13 (expressed as a residue bet

[Mellie]

(a) Find the inverse of 7 modulo 13 (expressed as a residue between 0 and the modulus) or answer 0 if the inverse does not exist.

(b)
Find the inverse of 8 modulo 35 (expressed as a residue between 0 and the modulus) or answer 0 if the inverse does not exist.

(c)
Find the inverse of 3 modulo 100 (expressed as a residue between 0 and the modulus) or answer 0 if the inverse does not exist.

(d)
Find the inverse of 15 modulo 18 (expressed as a residue between 0 and the modulus) or answer 0 if the inverse does not exist.

(e)
Find the inverse of 42 modulo 43 (expressed as a residue between 0 and the modulus) or answer 0 if the inverse does not exist.

hi I am new to the website. Not entirely sure how this works yet!! Nice meeting you all!!

[Guest]

a mod b has an inverse if and only if a and b have 1 as their only common factor.
If the inverse exists you can use the extended euclidean algorithm to find the inverse
https://en.wikipedia.org/wiki/Extended_ ... _algorithm

a) 2
b) 22
c) 67
d) No inverse (common factor of 3)
e) 42

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Hope this helped,

R. Baber.