Question

Tìm x,y,z

3x=5y , 9z=7y và 3x-2y-4z=10

 

Answer 1

\(3x=5y\Rightarrow\dfrac{x}{5}=\dfrac{y}{3}\Rightarrow\dfrac{x}{15}=\dfrac{y}{9}\)

\(9z=7y\Rightarrow\dfrac{y}{9}=\dfrac{z}{7}\)

\(\Rightarrow\dfrac{x}{15}=\dfrac{y}{9}=\dfrac{z}{7}\)

Áp dụng TCDTSBN ta có:

\(\dfrac{x}{15}=\dfrac{y}{9}=\dfrac{z}{7}=\dfrac{3x-2y-4z}{45-18-28}=\dfrac{10}{-1}=-10\)

\(\dfrac{x}{15}=-10\Rightarrow x=-150\\ \dfrac{y}{9}=-10\Rightarrow y=-90\\ \dfrac{z}{7}=-10\Rightarrow z=-70\)