Question

40\x-30=20\y-15=28\z-21vax.y.z=22400

Answer 1

\(\frac{40}{x-30}=\frac{20}{y-15}=\frac{28}{z-21}\Leftrightarrow\frac{10}{x-30}=\frac{5}{y-15}=\frac{7}{z-21}\)

Nghịch đảo lại ta có:

\(\Leftrightarrow\frac{x-30}{10}=\frac{y-15}{5}=\frac{z-21}{7}\Leftrightarrow\frac{x}{10}-3=\frac{y}{5}-3=\frac{z}{7}-3\)

\(\Leftrightarrow\frac{x}{10}=\frac{y}{5}=\frac{z}{7}=P\)\(\Rightarrow x=10P;y=5P;z=7P\)(1)

Mà xyz = 22400 =>\(10P\cdot5P\cdot7P=22400\Rightarrow P^3=64\Rightarrow P=4\)

Từ (1) : \(x=10\cdot4=40;y=5\cdot4=20;z=7\cdot4=28.\)