Hello, I already read the wikipedia page about it and couldn’t understand much of it. I know that the modular multiplicative inverse of an integer **a** *mod* **m** will be an integer **x** such that **a.x mod m = 1** but other than that I can’t understand anything else like **how to use it** and **when to use it**. It can be really helpful to know this subject so I would really appreciate an explanation or a good source for one other than the wikipedia page.

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If m is a prime number (read : 10^9 + 7) then (a / b) m = (a m * b^(m - 2) m) m

For proof look up little Fermat’s theorem.

Also note that (a / b) m =/= (a m / (b m)) m, otherwise there would be no need for modular inverse.

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So basically modular inverse is used to calculate (a/b)%m…

Thanks, the answer was short but enlightening…