Bài 1: Tìm các số a,b,c biết:
a)\(\left\{{}\begin{matrix}a\left(a+b+c\right)=12\\b\left(a+b+c\right)=18\\c\left(a+b+c\right)=30\end{matrix}\right.\)
b) \(ab=\dfrac{3}{5};bc=\dfrac{4}{5};ac=\dfrac{3}{4}\)
c) \(\left\{{}\begin{matrix}ab=c\\bc=4a\\ac=9b\end{matrix}\right.\)