V
vvquang77


CM: tru` can bac hai cua 2<= x+y<=can bac hai cua 2
voi' x^2 +y^2 = 1
minh` lam` bai` nay` roi` nhung thay hay nen post len cho cac ban tham khao
voi' x^2 +y^2 = 1
minh` lam` bai` nay` roi` nhung thay hay nen post len cho cac ban tham khao