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What is the rule for this table?

X= 3,6,9

Y= 5, 10, 15

I cant figure it out for my sons 3rd grade math!

If you graph the data points (3, 5), (6, 10), and (9, 15), you can draw a straight line through them.

http://www.flickr.com/photos/dwread/8394748611/

The rule for the table is the equation of that line.

Use two of the points to calculate the slope of the line.

rise = 15 - 10 = 5

run = 9 - 6 = 3

slope = rise/run = 5/3

http://www.flickr.com/photos/dwread/8394748623/

Use the slope and one of the points (say, (6, 10)) to determine the equation of the line.

y - 10 = (5/3)(x - 6)

This equation is in "point-slope" form. However, "slope-intercept" form is more convenient for filling in a data table.

Convert the equation to slope-intercept form:

y = (5/3)x

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