Answer
We'll use the formula of slope-intercept form which is given by $y=mx+b$
Work Step by Step
Direct variation is represented by the equation $y=kx$
The formula of slope-intercept form is given by $y=mx+b$
An example when a linear equation represents a direct variation is $y=2x$.
An example where a linear equation does not represent a direct variation is $y=2x+5$.
Hence an equation in slope-intercept form only sometimes represents a direct variation.
