document.write( "Question 1123243: If {x=1,y=-1; {x=2,y=2; {x=3,y=c are the solutions to the equation ax+by+2=0, determine the value of c. \n" ); document.write( "

Algebra.Com's Answer #739537 by ikleyn(52794) $\"\"$ $\"About$

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document.write( "From the \"given\" part we have, substituting the values into equation\r\n" );
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document.write( " a -  b = = -2    (1)    (substituting  x= 1, y= -1 into equation)\r\n" );
document.write( "2a + 2b = = -2    (2)    (substituting  x= 2, y=  2 into equation)\r\n" );
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document.write( "Equivalently\r\n" );
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document.write( "2a - 2b = -4      (1')\r\n" );
document.write( "2a + 2b = -2      (2')\r\n" );
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document.write( "-------------------------------- Add the equations\r\n" );
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document.write( "4a = -4 - 2 = -6  ====>  a =  =  = -1.5\r\n" );
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document.write( "Then from (1)  b = a + 2 = 0.5.\r\n" );
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document.write( "Now we are in position to determine the value of c.\r\n" );
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document.write( "It is  -1.5*3 + 0.5*c + 2 = 0,   or   c =  = 5.\r\n" );
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document.write( "Answer.  c = 5.\r\n" );
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