hieutoan

tim n nguyen duong de n,n+1,n+2 la luy thua cua 1 so nguyen to

$\sum a(a-b)(a-c)\geq \sum ab(\sqrt{a}-\sqrt{b})^{2}$

$a,b,c>0 va abc=1. Tim so thuc k max de BDT sau dung: \sum \frac{a}{(b+c)^{k}}\geq \frac{3}{2^{k}}$

$a,b,c\geq 0.CMR:\sum a(a-b)(a-c)\geq \sum ab(\sqrt{a}-\sqrt{b})^{2}$