Question

 Tìm x , y , z khi :

\(3x=y;5y=4z\)       và      \(6x+7y+8z=456\)

Answer 1

Từ \(\hept{\begin{cases}3x=y\\5y=4z\end{cases}\Rightarrow\hept{\begin{cases}\frac{x}{1}=\frac{y}{3}\\\frac{y}{4}=\frac{z}{5}\end{cases}\Rightarrow}\hept{\begin{cases}\frac{x}{4}=\frac{y}{12}\\\frac{y}{12}=\frac{z}{15}\end{cases}\Rightarrow}\frac{x}{4}=\frac{y}{12}=\frac{z}{15}\Rightarrow\frac{6x}{24}=\frac{7y}{84}=\frac{8z}{120}=\frac{6x+7y+8z}{24+84+120}}\)

\(=\frac{456}{228}=2\)

=> x = 8 ; y = 24 ; z = 30