# Math Help - solve in N

1. ## solve in N

x , y , z is primes numbers
solve :
x^3=x^2+y^2+z^2

2. ## Re: solve in N

One obvious solution: x=y=z=3.

thak you
but how?

4. ## Re: solve in N

Originally Posted by dhiab
x , y , z is primes numbers
solve :
x^3=x^2+y^2+z^2
Use congruence mod 3.
[1] x = 0 (mod 3) then x = 3 and y^2 + z^2 = 18 which implies y = z = 3
[2] x = 1 (mod 3) then ......
[3] x = 2 (mod 3) then ......