## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

variation constant $=k=1.8$ Equation of variation: $y=1.8x$
$y$ varies directly as $x$ so the variation is direct. The equation of a direct variation is of the form $y=kx$ where $k$ is the constant of variation. To find the value of $k$ substitute the given values of $x$ and $y$ into $y=kx$ to obtain: $$y=kx \\0.9=k(0.5) \\\frac{0.9}{0.5}=\frac{k(0.5)}{0.5} \\1.8=k$$ Thus, the equation of the variation is $y=1.8x$.