20/01/31 05:01:39.74 84Vel6iJ.net
>>286
l^3 -27abc = (a^3+b^3+c^3 - 3abc) + 3c(a-b)^2 + 3a(b-c)^2 + 3b(c-a)^2
= (l/2){(a-b)^2 + (b-c)^2 + (c-a)^2} + 3c(a-b)^2 + 3a(b-c)^2 + 3b(c-a)^2
≧ 0,
20/01/31 05:01:39.74 84Vel6iJ.net
>>286
l^3 -27abc = (a^3+b^3+c^3 - 3abc) + 3c(a-b)^2 + 3a(b-c)^2 + 3b(c-a)^2
= (l/2){(a-b)^2 + (b-c)^2 + (c-a)^2} + 3c(a-b)^2 + 3a(b-c)^2 + 3b(c-a)^2
≧ 0,