Question

\(\dfrac{x}{3}=\dfrac{y}{2};\dfrac{y}{7}=\dfrac{z}{5}vàx-2y+z=9\)

giúp mik với ạ mình đg cần gấp thank 

Answer 1

=> \(\dfrac{x}{21}=\dfrac{y}{14}=\dfrac{z}{10}\)

Theo tc dãy tỉ số bằng nhau ta có 

\(\dfrac{x}{21}=\dfrac{y}{14}=\dfrac{z}{10}=\dfrac{x-2y+z}{21-28+10}=\dfrac{9}{3}=3\Rightarrow x=63;y=42;z=30\)

Answer 2

Ta có: \(\dfrac{x}{3}=\dfrac{y}{2};\dfrac{y}{7}=\dfrac{z}{5}\Rightarrow\dfrac{x}{21}=\dfrac{y}{14}=\dfrac{z}{10}\Rightarrow\dfrac{x}{21}=\dfrac{2y}{28}=\dfrac{z}{10}\)

AD t/c DTSBN, có: \(\dfrac{x}{21}=\dfrac{2y}{28}=\dfrac{z}{10}=\dfrac{x-2y+z}{21-28+10}=\dfrac{9}{3}=3\)

\(\Rightarrow\left\{{}\begin{matrix}\dfrac{x}{21}=3\\\dfrac{y}{14}=3\\\dfrac{z}{10}=3\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=63\\y=42\\z=30\end{matrix}\right.\)