Explanation:

x^2/by+cz  =y^2 /cz+ax  =z^2 /ax+by  =1
x^2 =by+cz
y^2 =cz+ax
z^2 =ax+by
a/a+x  + b/b+y  + c/c+z
multiplying by x, y, and z nem
=ax/ax+x^2 + by/by+y^2 + cz/cz +z^2
=ax/ax+by+cz +by/by+cz+ax +cz/cz+ax+by
=ax+by+cz/ax+by+cz
=1