Question

\(\dfrac{x}{y}=\dfrac{7}{3}\)va 5x - 2y = 87

tim x,y

Answer 1

Vì \(\dfrac{x}{y}=\dfrac{7}{3}\Rightarrow\dfrac{x}{7}=\dfrac{y}{3}\Rightarrow\dfrac{5x}{35}=\dfrac{2y}{6}\)

Áp dụng tính chất dãy tỉ số bằng nhau ta có:

\(\dfrac{5x}{35}=\dfrac{2y}{6}=\dfrac{5x-2y}{35-6}=\dfrac{87}{29}=3\)

\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{5x}{35}=3\Rightarrow\dfrac{x}{7}=3\Rightarrow x=21\\\dfrac{2y}{6}=3\Rightarrow\dfrac{y}{3}=3\Rightarrow y=9\end{matrix}\right.\)

Vậy ..................

Chúc bạn học tốt!