document.write( "Question 40985This question is from textbook
\n" ); document.write( ": Determine the point A(x,y) so that the points A(x,y), B(0,3) C(1,0), D(7,2) will be the vertices of a parallelogram.\r
\n" ); document.write( "\n" ); document.write( "I think it is A(5,6), but I am not sure. Thank you for your help.
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Algebra.Com's Answer #26424 by psbhowmick(878)\"\" \"About 
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Slope of CD = \"%282-0%29%2F%287-1%29+=+1%2F3\"
\n" ); document.write( "Slope of BC = \"%283-0%29%2F%280-1%29+=+-3\"
\n" ); document.write( "Slope of AB = \"%28y-3%29%2F%28x-0%29+=+%28y-3%29%2Fx\"
\n" ); document.write( "Slope of AD = \"%28y-2%29%2F%28x-7%29\"\r
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\n" ); document.write( "\n" ); document.write( "As ABCD is a parallelogram so AB and CD are parallel and hence their slopes equal.
\n" ); document.write( "So \"%28y-3%29%2Fx+=+1%2F3\"
\n" ); document.write( "or 3(y-3) = x
\n" ); document.write( "or x - 3y = -9 __________(1)\r
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\n" ); document.write( "\n" ); document.write( "Also AD and BC are parallel and hence their slopes equal.
\n" ); document.write( "So \"%28y-2%29%2F%28x-7%29+=+-3\"
\n" ); document.write( "or (y-2) = -3(x-7)
\n" ); document.write( "or y + 3x = 23 ____________(2)\r
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\n" ); document.write( "\n" ); document.write( "Multiplying (2) by 3 and adding with (1) we have
\n" ); document.write( "\"3%2A3x+%2B+x+=+23%2A3+-+9+=+69+-+9+=+60\"
\n" ); document.write( "or 10x = 60
\n" ); document.write( "or x = 6
\n" ); document.write( "Then from (2) we have \"y+=+23+-+3%2A6+=+5\"\r
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\n" ); document.write( "\n" ); document.write( "Hence the coordinates of A are (6,5).
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