document.write( "Question 1114538: Please help. Thank you.
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Algebra.Com's Answer #729468 by ikleyn(52852) $\"\"$ $\"About$

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document.write( "The condition that the vector  u = xi+2yj-8k  is perpendicular to the vector  v = 2i-j+k  is that their scalar product is equal to zero:\r\n" );
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document.write( "    x*2 - 2*y - 8 = 0.     (1)\r\n" );
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document.write( "The condition that the vector  u = xi+2yj-8k  is perpendicular to the vector  w = 3i+2j-4k  is that their scalar product is equal to zero:\r\n" );
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document.write( "    x*3 + 4y + 32 = 0.     (2)\r\n" );
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document.write( "Thus you have this system of 2 equations in 2 unknowns \r\n" );
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document.write( "    2x - 2y =   8          (1')\r\n" );
document.write( "    3x + 4y = -32          (2')\r\n" );
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document.write( "Apply the Elimination method.  For it, multiply eq(1') by 2.  Keep eq(2') as is:\r\n" );
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document.write( "    4x - 4y =  16          (1'')\r\n" );
document.write( "    3x + 4y = -32          (2'')\r\n" );
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document.write( "Now add equations (1'') and (2'')\r\n" );
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document.write( "    7x = 16 - 32  ====>  x = .\r\n" );
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document.write( "Then from eq(1')  2y = 2x-8 =  =  = .\r\n" );
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document.write( "Answer.  x= ,  y= .\r\n" );
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