Question

Tính tỷ số x/y biết : 2x - 9y/7x - 5y = 4/9 

Answer 1

Ta có: \(\dfrac{2x-9y}{7x-5y}=\dfrac{4}{9}\)

\(\Leftrightarrow18x-81y=28x-20y\)

\(\Leftrightarrow-10x=61y\)

hay \(\dfrac{x}{y}=\dfrac{-61}{10}\)

Answer 2

\(ĐKXĐ:x\ne\dfrac{5}{7}y\) 

\(\dfrac{2x-9y}{7x-5y}=\dfrac{4}{9}\Rightarrow9\left(2x-9y\right)=4\left(7x-5y\right)\Leftrightarrow18x-81y=28x-20y\Leftrightarrow28x-18x=20y-81y\Leftrightarrow10x=-61y\Rightarrow\dfrac{10x}{y}=-61\Rightarrow\dfrac{x}{y}=-\dfrac{61}{10}\)