cho tam giác ABC các đường cao h\(_a\), h\(_{_{ }b}\), h\(_c\) thoa man he thuc 3h\(_a\) = 2h\(_b\) + h\(_c\) . Tim he thuc giua a, b, c
A.\(\dfrac{3}{a}=\dfrac{2}{b}-\dfrac{1}{c}\) B. \(3a=2b+c\) C.\(3a=2b-c\) D.\(\dfrac{3}{a}=\dfrac{2}{b}+\dfrac{1}{c}\)