D
duynhan1


CM:
[TEX]\sqrt{a1^2+b1^2} + \sqrt{a2+b2^2 }+ ..........+ \sqrt{an^2+bn^2}\geq \sqrt{(a1+a2+...+an)^2+(b1+b2+.....+bn)^2}[/TEX]
[TEX]\sqrt{a1^2+b1^2} + \sqrt{a2+b2^2 }+ ..........+ \sqrt{an^2+bn^2}\geq \sqrt{(a1+a2+...+an)^2+(b1+b2+.....+bn)^2}[/TEX]