[Toán 7] Tỉ lệ thức

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thinh.trantoan

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dien0709

$\dfrac{15}{x-9}=\dfrac{20}{y-12}=\dfrac{40}{z-24}$ và $xy=1200$

$\dfrac{15}{x-9}=\dfrac{20}{y-12}$

=>$\dfrac{y-12}{x-9}=\dfrac{12}{9}=\dfrac{y-12+12}{x-9+9}=\dfrac{y}{x}=\dfrac{4}{3}$

Kết hợp với $xy=1200$=>$x=30 , y=40 , z=80$ hoặc $(x;y;z)=(-30;-40;-80)$
 
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