Justin R.

asked • 02/03/15

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How many ordered pairs of integers (x,y) satisfy x2 + y2 < 9?

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Mark M. answered • 02/03/15

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The possible integers, for both x and y, are
 
-2, -1, 0, 1, 2                | x | < 3, | y | < 3
 
From these 20 possible combinations are possible. 5C2 = 20.
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Jon P.

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Shouldn't it be 25?  They asked for ordered pairs, not combinations.
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02/03/15

Mark M.

Yes, you correct. Five choices for first number and five choices for second.
 
Thank you.
 
Mark
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02/03/15

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