4 sol)  ²=s(s-a)(s-b)(s-c)²/s=(s-a)(s-b)(s-c)=(s-a)(s-b)*(s-b)(s-c)*

                                                                          (s-c)(s-a).......(1)

   using  A.M>=G.M,

   (S-a)+(s-b)/2>=(s-a)(s-b) {[(b+c-a)/2]+[(a+c-b)/2]}/2>=(s-a)(s-b)

                                        c/2>=(s-a)(s-b)

                                        (s-a)(s-b)<=c/2.......(2)

       similarly,                      (s-b)(s-c)<=a/2.......(3)

                                          (s-c)(s-a)<=b/2........(4)

using  the  results  (2),  (3)  &(4) in (1)

²/s<=(c/2)(a/2)(b/2) ²<=s(abc/8)<=[(a+b+c)/2](abc/8)=(a+b+c)(abc)/16

 

hence,  <=(1/4)(a+b+c)(abc)