Question 1016812
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Find the equation for the circle with a diameter whose endpoints are (2,-2) and (-5,4).  ????
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The center is at (-1.5, 1).

Notice that -1.5 = {{{(2 + (-5))/2}}} and 1 = {{{(-2 + 4)/2}}}.

The square of the diameter is {{{7^2 + (-6)^2)}}} = 85.

Notice that 7 = 2 - (-5),  and  -6 = -2 - 4.

The equation of the circle is 

{{{(x+1.5)^2 + (y-1)^2}}} = {{{85/4}}}.

The radius of the circle is {{{sqrt(85)/2}}}.
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