Problem
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PROBLEM 171
My apologies for my delay in posting this latest problem.  Those of you interested in knowing the reason for my tardiness may wish to check out the results at www.ironmanwisconsin.com.

The graph of y = x2 is shown in blue on the left.  When a circle is dropped into this parabola, it will be tangent to the graph at two points if its radius is large enough, as the red circle, or at one point otherwise, as the green circle.  Find the radius, b,  of the largest circle which is tangent to the parabola at only one point.

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ã2003 Alberto L. Delgado