# Recursive order pairs

The following recursive definition defines a set Z or ordered pairs

B. (2,4) is in Z.
R1. If(x,y) is in Z with x < 10 and y <10, then (x+1, y+1) is in Z.
R2. If(x,y) is in Z with x > 1 and y < 10, then(x-1, y+1) is in Z.

Plot these ordered pairs in the xy-plane

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I just did first line

B. (2,4) belongs to Z
###### Who is Participating?

Commented:
Draw a quick grid (I did it in Excel, but paper works fine). Mark point 2,4 and then look at the rules and keep marking all the points that fit and see what you get.

I only got 19 points, by the way.
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Commented:
And what's stopping you from doing the next lines?  2 is less than 10 and greater than 1, and 4 is less than ten, so you have a couple obvious points right there, and another three in the generation after that, and so on.
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Commented:
I think you will wind up with 21 points.
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