[tex]\bf \begin{array}{rllll}
(-10&,&-17)\\
x&&y
\end{array}\\\\
-------------------------------\\\\
\qquad \qquad \textit{direct proportional variation}\\\\
\textit{\underline{y} varies directly with \underline{x}}\qquad \qquad y=kx\impliedby
\begin{array}{llll}
k=constant\ of\\
variation
\end{array}\\\\
-------------------------------\\\\[/tex]
[tex]\bf \textit{we know that }
\begin{cases}
x=-10\\
y=-17
\end{cases}\implies -17=-10k\implies \cfrac{-17}{-10}=k
\\\\\\
\cfrac{17}{10}=k\implies {1\frac{7}{10}=k}
\\\\\\
thus\qquad \qquad y=1\frac{7}{10}x[/tex]
