Cho a/(b - c) + b/(c - a) + c/(a - b) = 1, Cho a/b+c + b/c+a + c/a+b = 1, Cho (a/b+c)+(b/c+a)+(c/a+b)=1, Cho [a/(b+c)] + [b/(c+a)] + [c/(a+b)] =1, Cho a/b + c + b/ c + a + c/a + b = 1