document.write( "Question 1068273: Find an equation(s) of the circle(s) of radius 4 with center on the line 4x + 3y + 7 = 0 and tangent to 3x + 4y + 34 = 0
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Algebra.Com's Answer #683504 by Fombitz(32388)\"\" \"About 
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Find the line perpendicular to the tangent line that goes through the circle center.
\n" ); document.write( "\"3x%2B4y%2B34=0\"
\n" ); document.write( "\"4y=-3x-34\"
\n" ); document.write( "\"y=-%283%2F4%29x-17%2F2\"
\n" ); document.write( "Perpendicular lines have slopes that are negative reciprocals.
\n" ); document.write( "\"-%283%2F4%29m%5B2%5D=-1\"
\n" ); document.write( "\"m%5B2%5D=4%2F3\"
\n" ); document.write( "Let the circle center be located at (h,k) and let the intersection point of the tangent line and the perpendicular line be (a,b).
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\n" ); document.write( "So you know that,
\n" ); document.write( "1.\"3a%2B4b%2B34=0\"
\n" ); document.write( "2.\"4h%2B3k%2B7=0\"
\n" ); document.write( "The perpendicular line goes through both (h,k) and (a,b) so,
\n" ); document.write( "3.\"k-b=%284%2F3%29%28h-a%29\"
\n" ); document.write( "and from the distance formula,
\n" ); document.write( "\"4%5E2=%28h-a%29%5E2%2B%28k-b%29%5E2\"
\n" ); document.write( "4.\"%28h-a%29%5E2%2B%28k-b%29%5E2=16\"
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\n" ); document.write( "Substitute 3 into 4,
\n" ); document.write( "\"%28h-a%29%5E2%2B%2816%2F9%29%28h-a%29%5E2=16\"
\n" ); document.write( "\"%2825%2F9%29%28h-a%29%5E2=16\"
\n" ); document.write( "\"%28h-a%29%5E2=%2816%2A9%29%2F25\"
\n" ); document.write( "\"h-a=+0+%2B-+12%2F5\"
\n" ); document.write( "First case,
\n" ); document.write( "\"h=a+%2B+12%2F5\"
\n" ); document.write( "So then going back through the equations and substituting for h,
\n" ); document.write( "5. \"3a%2B4b=-34\"
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\n" ); document.write( "\"4h%2B3k%2B7=0\"
\n" ); document.write( "\"4%28a%2B12%2F5%29%2B3k=-7\"
\n" ); document.write( "\"4a%2B3k=-7-12%2F5\"
\n" ); document.write( "6.\"4a%2B3k=-83%2F5\"
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\n" ); document.write( "\"k-b=%284%2F3%29%2812%2F5%29\"
\n" ); document.write( "7.\"k-b=16%2F5\"
\n" ); document.write( "You have three equations, three unknowns, using Cramer's rule,
\n" ); document.write( "\"a=-2%2F5\"
\n" ); document.write( "\"h=-41%2F5\"
\n" ); document.write( "\"k=-5\"
\n" ); document.write( "and then,
\n" ); document.write( "\"h=-2%2F5+%2B+12%2F5\"
\n" ); document.write( "\"h=10%2F5\"
\n" ); document.write( "\"h=2\"
\n" ); document.write( "So the first circle is,
\n" ); document.write( "\"highlight%28%28x-2%29%2B%28y%2B5%29%5E2=16%29\"
\n" ); document.write( "and
\n" ); document.write( "Second case,
\n" ); document.write( "\"h=a+-+12%2F5\"
\n" ); document.write( "Again substituting as needed for h,
\n" ); document.write( "8. \"3a%2B4b=-34\"
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\n" ); document.write( "\"4%28a-12%2F5%29%2B3k%2B7=0\"
\n" ); document.write( "\"4a%2B3k=-7%2B48%2F5\"
\n" ); document.write( "9.\"4a%2B3k=13%2F5\"
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\n" ); document.write( "\"k-b=%284%2F3%29%28-12%2F5%29\"
\n" ); document.write( "10.\"k-b=-16%2F5\"
\n" ); document.write( "Again you have three equations, three unknowns, using Cramer's rule,
\n" ); document.write( "\"a=754%2F35\"
\n" ); document.write( "\"h=-863%2F35\"
\n" ); document.write( "\"k=-195%2F7\"
\n" ); document.write( "and then,
\n" ); document.write( "\"h=a+-+12%2F5\"
\n" ); document.write( "\"h=754%2F35-12%2F5\"
\n" ); document.write( "\"h=134%2F7\"
\n" ); document.write( "So the second circle is,
\n" ); document.write( "\"highlight%28%28x-134%2F7%29%2B%28y%2B195%2F7%29%5E2=16%29\"
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