Question

Write an equation of the direct variation that includes the point (–8, 10).

Answer 1

`\bf \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\\ \qquad variation \end{array}\\\\ -------------------------------\\\\ \textit{we also know that }(~\stackrel{x}{-8}~,~\stackrel{y}{10}~)\implies 10=k(-8) \\\\\\ \cfrac{10}{-8}=k\implies \cfrac{5}{-4}=k\qquad therefore\qquad \boxed{y=-\cfrac{5}{4}x}`