Z
zenko_lady_hp


tren toa do Oxyz cho 2 diem A(1,2,3),B(4,4,5).tim toa do giao diem P cua duong thang AB va (OXY).chung to voi moi diem Q thuoc mat phang (xoy),bieu thuc /QA-QB/ co gia tri max khi Q trung P