Can you explain how to solve this:
1+2+2^2+2^(-1) mod 9

Question

Can you explain how to solve this: 
1+2+2^2+2^(-1) mod 9

anonymous · Answer

yes

anonymous · Answer

the only question is what does $2^{-1}$  mean in this context. it is clearly not $\frac{1}{2}$ but rather the multiplicative inverse of 2

anonymous · Answer

yes, this means inverse (but i don't really know what does it mean)

anonymous · Answer

it means then number between 0 and 8 which, when multiplied by 2, will be 1 mod 9

anonymous · Answer

you should be able to find it with no problem
keep multiplying 2 by successive integers, when you get a number that leaves a remainder of 1 when divided by 9, that is your answer

anonymous · Answer

so, how do I approach to this kind of question? should I do a summation of all numbers like 1+2+2^2 or how?