Examples

$x = 5$ , $y = - 1$

Step 1

When two variable quantities have a constant ratio, their relationship is called a direct variation. It is said that one variable varies directly as the other. The formula for direct variation is $y = k x$ , where $k$ is the constant of variation.

$y = k x$

Step 2

Solve the equation for $k$ , the constant of variation.

$k = \frac{y}{x}$

Step 3

Replace the variables $x$ and $y$ with the actual values.

$k = \frac{- 1}{5}$

Step 4

Move the negative in front of the fraction.

$k = - \frac{1}{5}$

Step 5

Use the direct variation model to create the equation.

$y = k x$

Step 6

Substitute the value of $k$ into the direct variation model.

$y = (- \frac{1}{5}) \cdot x$

Step 7

Simplify the result to find the direct variation equation.

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

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