document.write( "Question 175453: point C lies on line AB such that AC= 3/4 AB. If the endpoints of line AB are A(8,12) and B(-4,0) ,find C.\r
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\n" ); document.write( "\n" ); document.write( " i know i have to use substitution but its been a couple months since I have had a problem like this. If you could please guide me through the steps you would be very helpful. Thank You
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Algebra.Com's Answer #130575 by psbhowmick(878)\"\" \"About 
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If straight line AB is divided by the point such that AC:CB = m:n then the projections of AB on x and y axes will also be divided in the same ratio.\r
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\n" ); document.write( "\n" ); document.write( "Let the coordinates of the points be denoted by the name of the point with a suffix x or y. Thus coordinates of C are (\"C%5Bx%5D\",\"C%5By%5D\") and so on.\r
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\n" ); document.write( "\n" ); document.write( "Considering the projection on x axis,
\n" ); document.write( "\"%28A%5Bx%5D+-+C%5Bx%5D%29%2F%28C%5Bx%5D+-+B%5Bx%5D%29+=+m%2Fn\"
\n" ); document.write( "\"n%28A%5Bx%5D+-+C%5Bx%5D%29+=+m%28C%5Bx%5D+-+B%5Bx%5D%29\"
\n" ); document.write( "\"C%5Bx%5D+=+%28n%2AA%5Bx%5D+%2B+m%2AB%5Bx%5D%29%2F%28m%2Bn%29\" ___________ (1)\r
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\n" ); document.write( "\n" ); document.write( "In a similar way, \"C%5By%5D+=+%28n%2AA%5By%5D+%2B+m%2AB%5By%5D%29%2F%28m%2Bn%29\" ____________ (2)\r
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\n" ); document.write( "\n" ); document.write( "If the point lies outside the line segment AB then m/n will be negative as AC and CB will be in opposite directions.\r
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\n" ); document.write( "\n" ); document.write( "Here, \"A%5Bx%5D+=+8\", \"A%5By%5D+=+12\", \"B%5Bx%5D+=+-4\", \"B%5By%5D+=+0\" and m/n = +- 3 (- sign comes because C may be outside the line segment AB as well). Let m = +-3k and n = k (k = arbitrary constant).\r
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\n" ); document.write( "\n" ); document.write( "Substituting these in (1) we have
\n" ); document.write( "\"C%5Bx%5D+=+%28k%2A8+%2B-+3k%2A%28-4%29%29%2F%28%2B-3k+%2B+k%29\"
\n" ); document.write( "Either \"C%5Bx%5D+=+%288k+-+12k%29%29%2F%283k+%2B+k%29\" or \"C%5Bx%5D+=+%288k+%2B+12k%29%29%2F%28-3k+%2B+k%29\"
\n" ); document.write( "Either \"C%5Bx%5D+=+-1\" or \"C%5Bx%5D+=+-10\"\r
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\n" ); document.write( "\n" ); document.write( "Substituting into (2) we have
\n" ); document.write( "Either \"C%5By%5D+=+3\" or \"C%5By%5D+=+-6\"\r
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\n" ); document.write( "\n" ); document.write( "So the possible set of coordinates of C are (-1, 3) and (-10, -6).\r
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