Question

Tìm y là số nguyên :

\(y\dfrac{5}{y}=\dfrac{86}{y}\) (\(y\dfrac{5}{y}\) là hỗn số)

Answer 1

\(y\dfrac{5}{y}=\dfrac{86}{y}\)

\(\Leftrightarrow\dfrac{y^2+5}{y}=\dfrac{86}{y}\left(y\ne0\right)\)

\(\Leftrightarrow y^2+5=86\)

\(\Leftrightarrow y^2=81\)

\(\Leftrightarrow y=\pm9\)

Answer 2

\(y\dfrac{5}{y}=\dfrac{86}{y}\\ \Rightarrow\dfrac{y^2+5}{y}=\dfrac{86}{y}\\ \Rightarrow y^2+5=86\\ \Rightarrow y^2=81\\ \Rightarrow\left[{}\begin{matrix}y=9\\y=-9\end{matrix}\right.\)

Vậy \(y\in\left\{-9;9\right\}\)

Answer 3

`y 5/y = 86/y`

`(y.y +5)/y=86/y`

`y^2 + 5=86`

`y^2=81`

`y=9`