C# ModPow -1 problems

Question

I was trying this:

BigInteger.ModPow(x, -1, z);

But this method can't use -1 as Pow argument. Is there any already implemented class in C# that can do that, or I need to make my own class ?

Answer 1

Keep your highschool math book identity in mind: x ^ -1 == 1/x. So this is simply:

  BigInteger.DivRem(BigInteger.Divide(BigInteger.One, x), z, out remainder);