\(\frac{-13}{15}< \frac{y}{5}< \frac{-13}{21}\)
\(\frac{-13}{15}=\frac{-13.7}{15.7}=\frac{-91}{105}\)
\(\frac{y}{5}=\frac{21.y}{5.21}=\frac{21y}{105}\)
\(\frac{-13}{21}=\frac{-13.5}{21.5}=\frac{-65}{105}\)
=>\(\frac{-91}{105}< \frac{21y}{105}< \frac{-65}{105}\)
=> \(-91< 21y< -65\)
=> \(y=-4\)
Vì 21.(-4)=-84 (-91<-84<-65)
=>\(y=-4\)
Chúc bạn học tốt!
có \(-\frac{13}{15}< \frac{y}{5}< -\frac{13}{21}\)
\(\Leftrightarrow-\frac{91}{105}< \frac{21y}{105}< -\frac{65}{105}\)
\(\Rightarrow\hept{\begin{cases}-91< 21y< -65\\21y⋮21\end{cases}}\)
vì y thuộc Z
\(\Rightarrow21y=-84\)
\(\Rightarrow y=-4\)
