Question

x/y=2/7 và -3x+5y=58

Answer 1

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

Áp dụng t/c...

\(\dfrac{x}{2}=\dfrac{y}{7}=\dfrac{3x}{6}=\dfrac{5y}{35}=\dfrac{-3x+5y}{-6+35}=\dfrac{58}{29}=2\\ \Rightarrow\left\{{}\begin{matrix}x=4\\y=14\end{matrix}\right.\)

Answer 2

\(\dfrac{x}{y}=\dfrac{2}{7}\Rightarrow\dfrac{x}{2}=\dfrac{y}{7}\)

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

\(\dfrac{x}{2}=\dfrac{y}{7}\Rightarrow\dfrac{-3x+5y}{-6+35}=\dfrac{58}{29}=2\)

\(\dfrac{x}{2}=2\Rightarrow x=4\\ \dfrac{y}{7}=2\Rightarrow y=14\)

Answer 3

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

Áp dụng t/c của dãy số bằng nhau, ta có: \(\dfrac{5y+\left(-3x\right)}{35+\left(-6\right)}=\dfrac{58}{29}=2\)

\(\dfrac{y}{7}=2\Rightarrow y=14\)

\(\dfrac{x}{2}=2\Rightarrow x=4\)