<img src='/forum/images/emotion/icon_smile_rose.gif' border=0 align=middle><img src='/forum/images/emotion/icon_smile_rose.gif' border=0...
3(a^4 +b^4 +c^4) >= ( a^2 + b^2 + c^2) ^2 >= { 2(ab+bc+ca)}^2<br>= 4^2 = 16<br>vay> <br>a^4 + b^4 + c^4 >= 16/3<br>dung'' hok nhi?<img...
co'' moi cong thuc'' tong? wat'' la` <br> n(n-1) : 2 ma` thoi<br> <img...
Giãn cách tên bằng dấu phẩy(,).