If (a + b - c)/c = (a - b + c)/b = (-a + b + c)/a = k, then, for instance, (a + b - c)/c = k, so a + b - c = kc, so a + b = c(k + 1). Where might this lead one's investigation?If a,b,c are positive real numbers said that a+b-c/c=a-b+c/b=-a+b+c/a. find the value of (a+b)(b+c)(c+a)/abc