Question

if the value of "y" varies directly with "x" and y= -8 when x=20, find "y" if x= -4enter the number that belongs in the green box. reduce to the simplest form. y= ?/?

Answer 1

Explanation:

Direct variation means that the relation between the two variables is:

$y=kx$

k is called constant of proportionality. To find it we have to replace a pair of values x and y and then solve for k. We're given y = -8 and x = 20:

$\begin{gathered} -8=k\cdot20 \\ k=\frac{-8}{20}=-\frac{2}{5} \end{gathered}$

Therefore the relation is:

$y=-\frac{2}{5}x$

Now, if we replace x = -4:

$y=-\frac{2}{5}\cdot(-4)=\frac{2\cdot4}{5}=\frac{8}{5}$

Answer:

$y=\frac{8}{5}$