document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=92620>Question 92620</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Solve the system of equations:{3x+9y=7}<BR>\n" );
document.write( "                               {2x+6y=1} </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #67425 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=67425\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <TABLE  BORDER=1>\n" );
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document.write( " <TR><TD  ALIGN=MIDDLE>Solved by <A  rel=nofollow HREF=http://wiki.algebra.com/index.php/Tutoring_-_pluggable_solvers>pluggable</A> solver: <A  rel=nofollow HREF=solving_linear_system_by_substitution.solver>Solving a linear system of equations by subsitution</A></TD></TR>\n" );
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document.write( "  Lets start with the given system of linear equations<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2Ax%2B9%2Ay=7 ALIGN=MIDDLE  ALT=\"3%2Ax%2B9%2Ay=7\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2Ax%2B6%2Ay=1 ALIGN=MIDDLE  ALT=\"2%2Ax%2B6%2Ay=1\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "  Now in order to solve this system by using substitution, we need to solve (or isolate) one variable. I'm going to choose y.<BR>\n" );
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document.write( "  Solve for y for the first equation <BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=9%2Ay=7-3%2Ax ALIGN=MIDDLE  ALT=\"9%2Ay=7-3%2Ax\"   DISABLED_style= \"max-width:90%; height:auto;\" >Subtract <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2Ax ALIGN=MIDDLE  ALT=\"3%2Ax\"   DISABLED_style= \"max-width:90%; height:auto;\" > from both sides<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y=%287-3%2Ax%29%2F9 ALIGN=MIDDLE  ALT=\"y=%287-3%2Ax%29%2F9\"   DISABLED_style= \"max-width:90%; height:auto;\" > Divide both sides by 9. <BR>\n" );
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document.write( "  Which breaks down and reduces to <BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y=7%2F9-%281%2F3%29%2Ax ALIGN=MIDDLE  ALT=\"y=7%2F9-%281%2F3%29%2Ax\"   DISABLED_style= \"max-width:90%; height:auto;\" > Now we've fully isolated y<BR>\n" );
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document.write( "  Since y equals <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=7%2F9-%281%2F3%29%2Ax ALIGN=MIDDLE  ALT=\"7%2F9-%281%2F3%29%2Ax\"   DISABLED_style= \"max-width:90%; height:auto;\" > we can substitute the expression <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=7%2F9-%281%2F3%29%2Ax ALIGN=MIDDLE  ALT=\"7%2F9-%281%2F3%29%2Ax\"   DISABLED_style= \"max-width:90%; height:auto;\" > into y of the 2nd equation. This will eliminate y so we can solve for x.<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2Ax%2B6%2Ahighlight%28%287%2F9-%281%2F3%29%2Ax%29%29=1 ALIGN=MIDDLE  ALT=\"2%2Ax%2B6%2Ahighlight%28%287%2F9-%281%2F3%29%2Ax%29%29=1\"   DISABLED_style= \"max-width:90%; height:auto;\" > Replace y with <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=7%2F9-%281%2F3%29%2Ax ALIGN=MIDDLE  ALT=\"7%2F9-%281%2F3%29%2Ax\"   DISABLED_style= \"max-width:90%; height:auto;\" >. Since this eliminates y, we can now solve for x.<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2Ax%2B6%2A%287%2F9%29%2B6%28-1%2F3%29x=1 ALIGN=MIDDLE  ALT=\"2%2Ax%2B6%2A%287%2F9%29%2B6%28-1%2F3%29x=1\"   DISABLED_style= \"max-width:90%; height:auto;\" > Distribute 6 to <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=7%2F9-%281%2F3%29%2Ax ALIGN=MIDDLE  ALT=\"7%2F9-%281%2F3%29%2Ax\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2Ax%2B42%2F9-%286%2F3%29%2Ax=1 ALIGN=MIDDLE  ALT=\"2%2Ax%2B42%2F9-%286%2F3%29%2Ax=1\"   DISABLED_style= \"max-width:90%; height:auto;\" > Multiply<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2Ax%2B14%2F3-2%2Ax=1 ALIGN=MIDDLE  ALT=\"2%2Ax%2B14%2F3-2%2Ax=1\"   DISABLED_style= \"max-width:90%; height:auto;\" > Reduce any fractions<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2Ax-2%2Ax=1-14%2F3 ALIGN=MIDDLE  ALT=\"2%2Ax-2%2Ax=1-14%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > Subtract <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=14%2F3 ALIGN=MIDDLE  ALT=\"14%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > from both sides<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2Ax-2%2Ax=3%2F3-14%2F3 ALIGN=MIDDLE  ALT=\"2%2Ax-2%2Ax=3%2F3-14%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > Make 1 into a fraction with a denominator of 3<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2Ax-2%2Ax=-11%2F3 ALIGN=MIDDLE  ALT=\"2%2Ax-2%2Ax=-11%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > Combine the terms on the right side<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=0%2Ax=-11%2F3 ALIGN=MIDDLE  ALT=\"0%2Ax=-11%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > Now combine the terms on the left side.  <BR>\n" );
document.write( "   <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=0%2F1=-11%2F3 ALIGN=MIDDLE  ALT=\"0%2F1=-11%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > Since this expression is not true, we have an inconsistency. <BR>\n" );
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document.write( "  So there are no solutions. The simple reason is the 2 equations represent 2 parallel lines that will never intersect. Since no intersections occur, no solutions exist.<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+graph%28+500%2C+600%2C+-6%2C+5%2C+-10%2C+10%2C+%287-3%2Ax%29%2F9%2C+%281-2%2Ax%29%2F6+%29+ ALIGN=MIDDLE  ALT=\"+graph%28+500%2C+600%2C+-6%2C+5%2C+-10%2C+10%2C+%287-3%2Ax%29%2F9%2C+%281-2%2Ax%29%2F6+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > graph of <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2Ax%2B9%2Ay=7 ALIGN=MIDDLE  ALT=\"3%2Ax%2B9%2Ay=7\"   DISABLED_style= \"max-width:90%; height:auto;\" > (red) and <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2Ax%2B6%2Ay=1 ALIGN=MIDDLE  ALT=\"2%2Ax%2B6%2Ay=1\"   DISABLED_style= \"max-width:90%; height:auto;\" > (green) (hint: you may have to solve for y to graph these)<BR>\n" );
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document.write( "  and we can see that the two equations are parallel and will never intersect. So this system is <a  rel=nofollow HREF=http://www.algebra.com/algebra/homework/coordinate/lessons/Types-of-systems-inconsistent-dependent-independent.lesson>inconsistent</a></TD></TR>\n" );
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