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Direct variation and slope intercept form

by Cindy
(Ocoee, Florida, US)

What are some examples of slope intercept form representing direct variation?


Answered by Karin on Algebra-Class.com

Hi Cindy,

Thank you for contributing to Algebra-class.com. Direct variation is when two variable quantities have a constant ratio. The formula for direct variation is:
y = kx where k is the constant of variation.

You asked for an example in slope intercept form. As you can see, direct variation is set up in slope intercept form.

y = kx is very similar to y = mx. With direct variation, the y-intercept is 0, so you won't have the "+b" portion of slope intercept form. The constant of variation (k) is very similar to the slope in slope intercept form.

Some examples of equations that represent direct variation are:

y = 5x

y = 1/2x

y = .3x

As you can see, these are all set up in slope intercept form (with a y-intercept of 0).

These equations are called "direct variation" because y varies directly with x. If x increases, then y increases as well. If x decreases, then y decreases.

I hope this helps.


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