document.write( "Question 969255: Write the equation of the circle satisfying the given condition.
\n" ); document.write( "Radius of 2\"+sqrt%28+5+%29+\", tangent to y=2x and passing through (3,-4)
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Algebra.Com's Answer #592191 by Alan3354(69443)\"\" \"About 
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Write the equation of the circle satisfying the given condition.
\n" ); document.write( "Radius of \"2sqrt%285%29\", tangent to y = 2x and passing through (3,-4)
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\n" ); document.write( "The center has to be on the line parallel to y = 2x and \"2sqrt%285%29+=+sqrt%2820%29\" units from the line.
\n" ); document.write( "Find the line's equation:
\n" ); document.write( "y = 2x has a slope of 2 and passes thru (0,0)
\n" ); document.write( "A line perpendicular to it (RS) thru (0,0) is y = -x/2
\n" ); document.write( "A point on the line RS sqrt(20) from (0,0) is the intersection of a circle centered at (0,0) with r = sqrt(20)
\n" ); document.write( "--> x^2 + y^2 = 20
\n" ); document.write( "y = -x/2
\n" ); document.write( "x^2 + x^2/4 = 20
\n" ); document.write( "x = 4 (Ignore the x = -4 in Q2, (3,-4) is in Q4)
\n" ); document.write( "--> (4,-2)
\n" ); document.write( "The center of the circle is on a line thru (4,-2) with m = 2 (parallel to y = 2x)
\n" ); document.write( "y+2 = 2(x-4) = 2x - 8
\n" ); document.write( "y = 2x - 10
\n" ); document.write( "----
\n" ); document.write( "Find the point(s) sqrt(20) from (3,-4) on the line y = 2x - 10
\n" ); document.write( "It's the intersections of a circle centered at (3,-4) r = sqrt(20)
\n" ); document.write( "---
\n" ); document.write( "\"x-3%29%5E2+%2B+%28y%2B4%29%5E2+=+20\"
\n" ); document.write( "Sub for y
\n" ); document.write( "\"%28x-3%29%5E2+%2B+%282x-6%29%5E2+=+20\"
\n" ); document.write( "\"%28x-3%29%5E2+%2B+4%28x-3%29%5E2+=+20\"
\n" ); document.write( "\"%28x-3%29%5E2+=+4\"
\n" ); document.write( "x = 5 --> center @ (5,0) --> \"%28x-5%29%5E2+%2B+y%5E2+=+20\" ** Circle #1
\n" ); document.write( "----
\n" ); document.write( "x = 1 --> center @ (1,-8) --> \"%28x-1%29%5E2+%2B+%28y%2B8%29%5E2+=+20\" ** Circle #2
\n" ); document.write( "=============================
\n" ); document.write( "There must be an easier way to do this, but I don't know of one.
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