Question

[Võ Lê Phương Uyên]

40/x-30=20/y-15=28/z-21 và xyz=22400

Answer 1

[Kim Ngân]

$\frac{40}{x-30}=\frac{20}{y-15}=\frac{28}{z-21}\iff \frac{x-30}{40}=\frac{y-15}{20}=\frac{z-21}{28}$

$\Rightarrow \frac{x-30}{10}=\frac{y-15}{5}=\frac{z-21}{7}$

$\Rightarrow \frac{x}{10}-\frac{30}{10}=\frac{y}{5}-\frac{15}{5}=\frac{z}{7}-\frac{21}{7}$

$\Rightarrow \frac{x}{10}-3=\frac{y}{5}-3=\frac{z}{7}-3$

$\Rightarrow \frac{x}{10}=\frac{y}{5}=\frac{z}{7}$

Đặt: $\frac{x}{10}=\frac{y}{5}=\frac{z}{7}=t\Rightarrow \{\begin{array}{c}x=10t\\ y=5t\\ z=7t\end{array}$

$xyz=22400\iff 350t^3=22400\iff t^3=64\Rightarrow t=4$

$\Rightarrow \{\begin{array}{c}x=40\\ y=20\\ z=28\end{array}$




 

Answer 2

[Kim Ngân]

Ớ bài này mình lm sai ạ !