Posted by **Mary** on Friday, November 2, 2007 at 4:54pm.

I need a function rule for the following:

X Y

-2 -2

0 1

1 2

- Algebra -
**drwls**, Friday, November 2, 2007 at 6:41pm
Well, it's not a straight line, since the change is y is not proportional the change in x. You could fit a very large number of functions to those threee points, but the simplest would be a parabola of the form

y = ax^2 + bx + c

You can use your three data points to solve for a, b and c.

-2 = 4a - 2b + c

1 = c

2 = a + 4b + c

This tells you right away what c is, so now you can solve for a and b

- Algebra -
**drwls**, Saturday, November 3, 2007 at 1:10am
I know what you are asking for. A function of the form y = mx + b won't fit all three points. That is why I chose a quadratic fucntion. Try completing what I started

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