Question

Tìm cặp số x, y biết : 1+3y/12 = 1+5y/5x = 1+7y/4x

 

Answer 1

\(\frac{1+3y}{12}=\frac{1+5y}{5x}=\frac{1+7y}{4x}\)

\(\Rightarrow\frac{1+5y}{5x}=\frac{1+7y}{4x}=\frac{1+5y-1+7y}{\left(5x-4x\right)}=-\frac{2y}{x}\)

\(\frac{1+5y}{5}=-2y\)

Giải ra ta có : \(y=-\frac{1}{15}\)

\(\Leftrightarrow x=2\)

Answer 2

\(\frac{1+3y}{12}=\frac{1+5y}{5x}=\frac{1+7y}{4x}\)

Ta có : \(\frac{1+5y}{5x}=\frac{1+7y}{4x}\)

\(\Rightarrow\frac{\left(1+5y-1+7y\right)}{\left(5x-4x\right)}=\frac{-2y}{x}\)

\(\Rightarrow\frac{\left(1+5y\right)}{5}=-2y\)

Ta được \(y=\frac{-1}{15}\)

\(\Rightarrow x=2\)

 

Answer 3

x=2

y=-1/15

Answer 4

sao x=2 vậy?

Answer 5

\(\dfrac{1+5y}{5x}=\dfrac{1+7y}{4x}=\dfrac{1+5y-\left(1+7y\right)}{5x-4x}=\dfrac{1+5y-1-7y}{x}=\dfrac{-2y}{x}\Rightarrow y=\dfrac{-1}{15}\Rightarrow x=2\)