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 Thread: i need help please! View Single Post 04-01-2011   #4
MAS1   Join Date: Dec 2008
Posts: 249 Quote:
 Originally Posted by kimsoohanmoo Find the relation ship between the set of ordered pairs (-3, 7), (-1, 3), (3, -5), (4,-7) please help me with this Ive been stuck on this for a very, very long time. Im not looking to graph them I mean like (example) (4, 2), ...etc the relationship between them is that y is the square root of x. I know for the question I asked it isnt multiplication or division or the square root so it must be some sort of equation right. Ive been working on this for two days............. If you graph them you can see these coordinates form a line.

To check that it is a linear function look to see that there is a constant rate of change (slope) between the points.

(-3, 7), (-1, 3): m = (3 - 7) / (-1 - -3) = -4 / 2 = -2

(-1, 3), (3, -5): m = (-5 - 3) / (3 - -1) = -8 / 4 = -2

(3, -5), (4, -7): m = (-7 - -5) / (4 - 3) = -2 / 1 = -2

So yes, there is a constant rate of change between the points.
To find the equation try using point-slope form of a line.

First pick a point, say (4, -7). Point-slope form is y - y1 = m(x - x1).

Then y - -7 = -2(x - 4)
y + 7 = -2x + 8
y = -2x + 1
Hope this helps. 