Oops, there was a typographic error in the formula at the start of the month. It is right now. Thank you to Andrei Lazanu of school 205 Bucharest for what follows.

First, I tried to solve the problem in the "conventional mathematical way", and I listed the powers of 1, 2, 3, 4, 9 from 0 to 9, looking in each case to eliminate those greater than 5 digit numbers, attributed to both

rn

and

ch

Because it seemed very long, I tried the problem from a "calculatoristic" point of view:

First I observed that N must be greater than 0, and each other number must have the values from 0 to 9. I wrote a program in MATLAB to calculate the numbers.

The idea of the program is to test for all digits the values from 0 (1) to 9. For this I wrote a cycle allowing n to have values between 1 and 9. For each value of n , I give, in an inside cycle, to r values from 0 to 9. So, this works as follows: n has the value 1, and for this r has in turn values from 0 to 9. This is the idea of a cycle inside another one. Each cycle ends with end.

For this problem there are 5 cycles, the most interior being for h , that has values between 0 and 9.

When I arrived at this cycle, I test if the condition of the problem:

rn -i+ ch =1000×r+100×i+10×c+h

is fulfilled. If yes, the number

1000×r+100×i+10×c+h

is written on the screen.

Because this way I'll find all solutions, even with repeated digits, I must in a further step eliminate them.

Here is the program:

forn=1:9;

   forr=0:9;

       fori=0:9;

           forc=0:9;

               forh=0:9;

                   if rn -i+ ch -10000×n-1000×r-100×i-10×c-h==0

                       a=[nrich]

                   end

               end

           end

       end

   end

end

The results given were the following:

a = 5 9 0 5 0

and

a = 5 9 2 6 3

As in the first one the digits are not distinct, this is not a solution.

The second is the unique solution of the problem:

n = 5
r = 9
i = 2
c = 6
h = 3