document.write( "Question 678416: Find the equation of the circle if it is tangent to the line x+y=2 at point (4,-2) and the center at x-axis. \n" ); document.write( "
Algebra.Com's Answer #421400 by MathLover1(20849)\"\" \"About 
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\n" ); document.write( "\"%28x+-+h%29%5E+2+%2B+%28y+-+k%29+%5E2+=+r%5E2\"\r
\n" ); document.write( "\n" ); document.write( "(h,k)-center and r radius\r
\n" ); document.write( "\n" ); document.write( "given:\r
\n" ); document.write( "\n" ); document.write( "given:\r
\n" ); document.write( "\n" ); document.write( " the circle if it is tangent to the line \"x%2By=2\" at point (\"4\",\"-2\") and the center at \"x-axis\"\r
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\n" ); document.write( "\n" ); document.write( "find the equation of the circle:\r
\n" ); document.write( "\n" ); document.write( "Let ... C(\"a\",\"0\") be the center.\r
\n" ); document.write( "\n" ); document.write( "Also, let the line L :\"x%2By=2\" touch\r
\n" ); document.write( "\n" ); document.write( "this circle at the point A(\"4\",\"-2\")\r
\n" ); document.write( "\n" ); document.write( "Line \"x+%2B+y+=+2\" \"y+=+-%281%29x+%2B2\" has slope \"m%5B1%5D+=+-1\"\r
\n" ); document.write( "\n" ); document.write( "and slope of seg AC is \"m%5B2%5D+=+%28+-2-0+%29+%2F+%28+4+-a+%29+=+-2+%2F+%28+4-a+%29\".\r
\n" ); document.write( "\n" ); document.write( "Since line L is perpendicular to segment AC, \"+m%5B1%5D%2Am%5B2+%5D=+1\"\r
\n" ); document.write( "\n" ); document.write( "\"%28-1%29+%2A+%28-2+%2F+%28+4+-a+%29+%29+=+1\"\r
\n" ); document.write( "\n" ); document.write( "\"-2%2F+%28+4+-a+%29+=+1\"\r
\n" ); document.write( "\n" ); document.write( "\"-2=++4-a+\"\r
\n" ); document.write( "\n" ); document.write( "\"a+=+4%2B2\"\r
\n" ); document.write( "\n" ); document.write( "\"a+=+6\"\r
\n" ); document.write( "\n" ); document.write( "Hence, C ≡ (\"a\",\"0\") ≡ (\"6\",\"0\")\r
\n" ); document.write( "\n" ); document.write( "and \r
\n" ); document.write( "\n" ); document.write( "\"r%5E2+=+%28AC%29%5E2+=+%286-4%29%5E2+%2B+%280%2B2%29%5E2+=%282%29%5E2+%2B+%282%29%5E2+=+8\".\r
\n" ); document.write( "\n" ); document.write( "Hence, by Center-Radius Form, eq of circle is:\r
\n" ); document.write( "\n" ); document.write( "\"%28+x+-+h+%29%5E2+%2B+%28+y+-+k+%29%5E2++=+r%5E2+\"\r
\n" ); document.write( "\n" ); document.write( "\"%28+x+-+2+%29%5E2++%2B+%28+y+-+0+%29%5E2++=+8+\"\r
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\n" ); document.write( "\n" ); document.write( "\"%28+x+-+2+%29%5E2++%2B+y+%5E2++=+8\"......... your answer\r
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