document.write( "Question 1082737: I'm trying to solve the system using substitution. I don't understand it. The problem is ~ -7x-2y=-13
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Algebra.Com's Answer #696802 by ikleyn(52781) $\"\"$ $\"About$

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document.write( "-7x -2y = -13,   (1)\r\n" );
document.write( "x - 2y = 11      (2)\r\n" );
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document.write( "Look into equation (2). Express x = 11 + 2y from it.\r\n" );
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document.write( "Do you understand how I did it? - I simply added 2y to both sides of the equation (2).\r\n" );
document.write( "So, I obtained this: x = 11 + 2y.\r\n" );
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document.write( "Now I substutute it into equation (1), replacing x there:\r\n" );
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document.write( "-7*(11+2y) - 2y = -13.\r\n" );
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document.write( "It is a single equation for \"y\".\r\n" );
document.write( "It is much easier to solve it. Simplify:\r\n" );
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document.write( "-77 - 14y - 2y = -13,\r\n" );
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document.write( "-16y = -13 + 77,\r\n" );
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document.write( "-16y = 64  ---->  y =  = -4.\r\n" );
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document.write( "OK. We just found y= -4.\r\n" );
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document.write( "Now substitute it into equation (2). You will get\r\n" );
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document.write( "x - 2*(-4) = 11  ---->  x + 8 = 11  ---->  x = 11-8  ---->  x= 3.\r\n" );
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document.write( "Answer.  The solution is x= 3, y= -4.\r\n" );
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\n" ); document.write( "\n" ); document.write( "Do you understand this explanation ?\r
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\n" ); document.write( "\n" ); document.write( "If you do, then you know now how the substitution method works.\r
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\n" ); document.write( "To see more examples, look into this lesson\r
\n" ); document.write( "\n" ); document.write( " - Solution of a linear system of two equations in two unknowns by the Substitution method \r
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\n" ); document.write( "\n" ); document.write( "Also, you have this free of charge online textbook in ALGEBRA-I in this site\r
\n" ); document.write( "\n" ); document.write( " - ALGEBRA-I - YOUR ONLINE TEXTBOOK.\r
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\n" ); document.write( "\n" ); document.write( "The referred lesson is the part of this online textbook under the topic \"Systems of two linear equations in two unknowns\".\r
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