document.write( "Question 1140775: (1) A cirlce is defined by the equation x^2-6x+y^2-2y=6.\r
\n" ); document.write( "\n" ); document.write( "(a) Rewrite the equation of the circle in the form:(x-a)^2+(y-b)^2=r^2\r
\n" ); document.write( "\n" ); document.write( "(b) Write down the coordinates of M,the centre of the circle.\r
\n" ); document.write( "\n" ); document.write( "(c) A tangent PQ is drawn from the point P(6;-2) to the circle, with Q the point of contact.Calculate the length of the tangent PQ.\r
\n" ); document.write( "\n" ); document.write( "Please can someone please help me with the question I begg
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Algebra.Com's Answer #761289 by MathLover1(20850)\"\" \"About 
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(1) A cirlce is defined by the equation \"x%5E2-6x%2By%5E2-2y=6\". \r
\n" ); document.write( "\n" ); document.write( "(a) Rewrite the equation of the circle in the form:\r
\n" ); document.write( "\n" ); document.write( "\"%28x-a%29%5E2%2B%28y-b%29%5E2=r%5E2+\"\r
\n" ); document.write( "\n" ); document.write( "\"%28x%5E2-6x%29%2B%28y%5E2-2y%29=6\"............complete square\r
\n" ); document.write( "\n" ); document.write( "\"%28x%5E2-6x%2Bb%5E2%29-b%5E2%2B%28y%5E2-2y%2Bb%5E2%29-b%5E2=6\".......\"b\" for \"x\" part is \"6%2F2=3\" and \"b\" for \"y\" part is \"2%2F2=1\"\r
\n" ); document.write( "\n" ); document.write( "\"%28x%5E2-6x%2B3%5E2%29-3%5E2%2B%28y%5E2-2y%2B1%5E2%29-1%5E2=6\"\r
\n" ); document.write( "\n" ); document.write( "\"%28x-3%29%5E2-9%2B%28y-1%29%5E2-1=6\"\r
\n" ); document.write( "\n" ); document.write( "\"%28x-3%29%5E2%2B%28y-1%29%5E2-10=6\"\r
\n" ); document.write( "\n" ); document.write( "\"%28x-3%29%5E2%2B%28y-1%29%5E2=6%2B10\"\r
\n" ); document.write( "\n" ); document.write( "\"%28x-3%29%5E2%2B%28y-1%29%5E2=16\"\r
\n" ); document.write( "\n" ); document.write( "\"%28x-3%29%5E2%2B%28y-1%29%5E2=4%5E2\"\r
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\n" ); document.write( "\n" ); document.write( "(b) Write down the coordinates of M,the centre of the circle. \r
\n" ); document.write( "\n" ); document.write( "since \"a=3\" and \"b=1\",\r
\n" ); document.write( "\n" ); document.write( "the coordinates of M are: (\"a\",\"b\")=(\"3\",\"1\")\r
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\n" ); document.write( "\n" ); document.write( "(c) A tangent PQ is drawn from the point P(\"6\";\"-2\") to the circle, with \"Q\" the point of contact.Calculate the length of the tangent \"PQ\". \r
\n" ); document.write( "\n" ); document.write( "if \"PQ\" is a tangent, it is perpendicular to the radius\"+PM\"\r
\n" ); document.write( "\n" ); document.write( "points \"P\",\"Q\", and \"M\" form right triangle where \"QM\" is hypotenuse, \"PM\" and \"PQ\" are legs\r
\n" ); document.write( "\n" ); document.write( "we can find the length of \"PM+\"using points P(\"6\";\"-2\") and M(\"3\",\"1\")\r
\n" ); document.write( "\n" ); document.write( "\"PM=sqrt%28%283-6%29%5E2%2B%281-%28-2%29%29%5E2%29\"\r
\n" ); document.write( "\n" ); document.write( "\"PM=sqrt%28%28-3%29%5E2%2B%281%2B2%29%5E2%29\"\r
\n" ); document.write( "\n" ); document.write( "\"PM=sqrt%28%28-3%29%5E2%2B%283%29%5E2%29\"\r
\n" ); document.write( "\n" ); document.write( "\"PM=sqrt%289%2B9%29\"\r
\n" ); document.write( "\n" ); document.write( "\"PM=sqrt%282%2A9%29\"\r
\n" ); document.write( "\n" ); document.write( "\"PM=3sqrt%282%29\"->one leg\r
\n" ); document.write( "\n" ); document.write( "and \r
\n" ); document.write( "\n" ); document.write( "\"PQ\", the other leg will be: \r
\n" ); document.write( "\n" ); document.write( "P(\"6\";\"-2\") and Q(\"x\",\"y\")\r
\n" ); document.write( "\n" ); document.write( "\"PQ=sqrt%28%28x-6%29%5E2%2B%28y%2B2%29%5E2%29+\"\r
\n" ); document.write( "\n" ); document.write( "then we can find hypotenuse \"QM\":\r
\n" ); document.write( "\n" ); document.write( "\"M\"(\"3\",\"1\") and \"Q\"(\"x\",\"y\")\r
\n" ); document.write( "\n" ); document.write( "\"QM=sqrt%28%28x-3%29%5E2%2B%28y-1%29%5E2%29\" \r
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\n" ); document.write( "\n" ); document.write( "using Pythagorean theorem:\r
\n" ); document.write( "\n" ); document.write( "\r
\n" ); document.write( "\n" ); document.write( "\"%28x-3%29%5E2%2B%28y-1%29%5E2=%28x-6%29%5E2%2B%28y%2B2%29%5E2%2B18\"\r
\n" ); document.write( "\n" ); document.write( "\"x%5E2-6x%2B9%2By%5E2-2y%2B1=x%5E2-12x%2B36%2By%5E2%2B4y%2B4%2B18\"\r
\n" ); document.write( "\n" ); document.write( "\"-6x-2y%2B10=-12x%2B4y%2B58\"\r
\n" ); document.write( "\n" ); document.write( "\"-6x%2B12x=2y%2B4y%2B58-10\"\r
\n" ); document.write( "\n" ); document.write( "\"6x=6y%2B48\"\r
\n" ); document.write( "\n" ); document.write( "\"x=y%2B8\".............=>so point \"Q\"(\"y%2B8\",\"y\")\r
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\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "then substitute in Pythagorean theorem:\r
\n" ); document.write( "\n" ); document.write( "\r
\n" ); document.write( "\n" ); document.write( "\"%28y%2B5%29%5E2%2B%28y-1%29%5E2=%28y%2B2%29%5E2%2B%28y%2B2%29%5E2%2B18\"........solve for \"y\"\r
\n" ); document.write( "\n" ); document.write( "\"y%5E2%2B10y%2B25+%2By%5E2-2y%2B1=+y%5E2%2B4y%2B4%2By%5E2%2B4y%2B4%2B18\"\r
\n" ); document.write( "\n" ); document.write( "\"8y%2B26=+8y%2B26\"\r
\n" ); document.write( "\n" ); document.write( "\"y=0\"\r
\n" ); document.write( "\n" ); document.write( "and, then\r
\n" ); document.write( "\n" ); document.write( "\"+x=0%2B8\"=>\"x=8\"\r
\n" ); document.write( "\n" ); document.write( "so \"Q\"(\"+8\",\"0\")\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "the length of the tangent \"PQ\" is: distance between
\n" ); document.write( "\"P\"(\"6\";\"-2\")
\n" ); document.write( "\"Q\"(\"+8\",\"0\")\r
\n" ); document.write( "\n" ); document.write( "\"PQ=sqrt%28%288-6%29%5E2%2B%280%2B2%29+%29\"
\n" ); document.write( "\"PQ=sqrt%282%5E2%2B2%5E2%29\"
\n" ); document.write( "\"PQ=sqrt%282%2A2%5E2%29\"
\n" ); document.write( "\"PQ=2sqrt%282%29\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "double check:\r
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "\"%285%29%5E2%2B%28-1%29%5E2=%282%29%5E2%2B%282%29%5E2%2B18\"
\n" ); document.write( "\"25%2B1=4%2B4%2B18\"
\n" ); document.write( "\"26=26\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "tangent is a line passing through points P(\"6\";\"-2\") and \"Q\"(\"+8\",\"0\"), so find equation\r
\n" ); document.write( "\n" ); document.write( "first find a slope:\r
\n" ); document.write( "\n" ); document.write( "\"m=%280-%28-2%29%29%2F%288-6%29\"
\n" ); document.write( "\"m=2%2F2\"
\n" ); document.write( "\"m=1\"\r
\n" ); document.write( "\n" ); document.write( "and use slope point formula\r
\n" ); document.write( "\n" ); document.write( "\"y-y%5B1%5D=m%28x-x%5B1%5D%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y-0=1%28x-8%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y=x-8\"-> tangent line\r
\n" ); document.write( "\n" ); document.write( "line that passes through \"P+\"and\"+M\" is perpendicular to tangent and it is:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"m=%281-%28-2%29%29%2F%283-6%29\"
\n" ); document.write( "\"m=3%2F-3\"
\n" ); document.write( "\"m=-1\"\r
\n" ); document.write( "\n" ); document.write( "and use slope point formula\r
\n" ); document.write( "\n" ); document.write( "\"y-y%5B1%5D=m%28x-x%5B1%5D%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y-1=-1%28x-3%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y-1=-x+%2B3\"\r
\n" ); document.write( "\n" ); document.write( "\"y=-x+%2B3%2B1\"\r
\n" ); document.write( "\n" ); document.write( "\"y=-x+%2B4\"\r
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