document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=124914>Question 124914</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Solve the system by addition.	x + y = 9	x – y = 9 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #91554 by </B><A HREF=/tutors/aboutme.mpl?userid=bucky><B>bucky(2189)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=bucky><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=91554\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Given to solve:<BR>\n" );
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document.write( "x + y = 9<BR>\n" );
document.write( "x - y = 9<BR>\n" );
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document.write( "To solve these by addition you need to have a term in one of the equations equal in value<BR>\n" );
document.write( "but opposite in sign to the corresponding term in the other equation. This set of equations<BR>\n" );
document.write( "already has that done for you. You have + y in the top equation and -y in the bottom <BR>\n" );
document.write( "equation. Therefore, if you add these two equations in vertical columns on both sides, the<BR>\n" );
document.write( "+y of the top equation will cancel the -y of the bottom equation when they are added vertically.<BR>\n" );
document.write( "And in adding vertically you in the \"x\" column, you get x + x = 2x. Also on the other side<BR>\n" );
document.write( "of the equal signs when you add vertically you get 9 + 9 = 18. So the vertical addition of<BR>\n" );
document.write( "these two equations results in:<BR>\n" );
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document.write( "2x = 18<BR>\n" );
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document.write( "Solve for x by dividing both sides of this resulting equation by 2 (because 2 is the multiplier<BR>\n" );
document.write( "of x). When you divide both sides by 2 you get:<BR>\n" );
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document.write( "x = 9<BR>\n" );
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document.write( "That solves for x. You can solve for y by returning to one of the original two equations and<BR>\n" );
document.write( "substituting 9 for x in that equation. <BR>\n" );
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document.write( "Let's return to:<BR>\n" );
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document.write( "x + y = 9<BR>\n" );
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document.write( "Substitute 9 for x and the equation becomes:<BR>\n" );
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document.write( "9 + y = 9<BR>\n" );
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document.write( "Get rid of the 9 on the left side by subtracting 9 from both sides and the resulting<BR>\n" );
document.write( "equation is:<BR>\n" );
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document.write( "y = 0<BR>\n" );
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document.write( "So the answer to this problem is x = 9 and y = 0.<BR>\n" );
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document.write( "You can check this result by substitution 9 for x and 0 for y in the second equation to <BR>\n" );
document.write( "see if the left side of the resulting equation equals the right side. The second equation is:<BR>\n" );
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document.write( "x - y = 9<BR>\n" );
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document.write( "Substituting for x and y results in:<BR>\n" );
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document.write( "9 - 0 = 9<BR>\n" );
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document.write( "This is correct, so our answers for x and y are OK.<BR>\n" );
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document.write( "Hope this helps you to understand the problem a little better.<BR>\n" );
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document.write( " </SPAN>\n" );
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