a) \(2a=3b=4c\Rightarrow\dfrac{a}{6}=\dfrac{b}{4}=\dfrac{c}{3}\)
Áp dụng t/c dtsbn:
\(\dfrac{a}{6}=\dfrac{b}{4}=\dfrac{c}{3}=\dfrac{a-b+c}{6-4+3}=\dfrac{35}{5}=7\)
\(\Rightarrow\left\{{}\begin{matrix}a=7.6=42\\b=7.4=28\\c=7.3=21\end{matrix}\right.\)
b) \(3a=5b=8c\Rightarrow\dfrac{a}{40}=\dfrac{b}{24}=\dfrac{c}{15}\)
Áp dụng t/c dtsbn:
\(\dfrac{a}{40}=\dfrac{b}{24}=\dfrac{c}{15}=\dfrac{a+b+c}{40+24+15}=\dfrac{158}{79}=2\)
\(\Rightarrow\left\{{}\begin{matrix}a=40.2=80\\b=24.2=48\\c=15.2=30\end{matrix}\right.\)
c) \(\left\{{}\begin{matrix}\dfrac{a}{2}=\dfrac{b}{3}\\\dfrac{b}{5}=\dfrac{c}{4}\end{matrix}\right.\)\(\Rightarrow\dfrac{a}{10}=\dfrac{b}{15}=\dfrac{c}{12}\)
Áp dụng t/c dtsbn:
\(\dfrac{a}{10}=\dfrac{b}{15}=\dfrac{c}{12}=\dfrac{a-b+c}{10-15+12}=\dfrac{-49}{7}=-7\)
\(\Rightarrow\left\{{}\begin{matrix}a=\left(-7\right).10=-70\\b=\left(-7\right).15=-105\\c=\left(-7\right).12=-84\end{matrix}\right.\)
