document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=118518>Question 118518</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 3x+4y=12<BR>\n" );
document.write( "1x+4/3y=4 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #86665 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=86665\">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( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%281%29%2Ax%2B%284%2F3%29%2Ay=4 ALIGN=MIDDLE  ALT=\"%281%29%2Ax%2B%284%2F3%29%2Ay=4\"   DISABLED_style= \"max-width:90%; height:auto;\" > Start with the second equation<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%28%281%29%2Ax%2B%284%2F3%29%2Ay%29=%283%29%2A%284%29 ALIGN=MIDDLE  ALT=\"3%28%281%29%2Ax%2B%284%2F3%29%2Ay%29=%283%29%2A%284%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > Multiply both sides by the LCD 3<BR>\n" );
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document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2Ax%2B4%2Ay=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B4%2Ay=12\"   DISABLED_style= \"max-width:90%; height:auto;\" > Distribute and simplify<BR>\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%2B4%2Ay=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B4%2Ay=12\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2Ax%2B4%2Ay=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B4%2Ay=12\"   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=4%2Ay=12-3%2Ax ALIGN=MIDDLE  ALT=\"4%2Ay=12-3%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=%2812-3%2Ax%29%2F4 ALIGN=MIDDLE  ALT=\"y=%2812-3%2Ax%29%2F4\"   DISABLED_style= \"max-width:90%; height:auto;\" > Divide both sides by 4. <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=3-%283%2F4%29%2Ax ALIGN=MIDDLE  ALT=\"y=3-%283%2F4%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=3-%283%2F4%29%2Ax ALIGN=MIDDLE  ALT=\"3-%283%2F4%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=3-%283%2F4%29%2Ax ALIGN=MIDDLE  ALT=\"3-%283%2F4%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=3%2Ax%2B4%2Ahighlight%28%283-%283%2F4%29%2Ax%29%29=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B4%2Ahighlight%28%283-%283%2F4%29%2Ax%29%29=12\"   DISABLED_style= \"max-width:90%; height:auto;\" > Replace y with <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3-%283%2F4%29%2Ax ALIGN=MIDDLE  ALT=\"3-%283%2F4%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=3%2Ax%2B4%2A%283%29%2B4%28-3%2F4%29x=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B4%2A%283%29%2B4%28-3%2F4%29x=12\"   DISABLED_style= \"max-width:90%; height:auto;\" > Distribute 4 to <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3-%283%2F4%29%2Ax ALIGN=MIDDLE  ALT=\"3-%283%2F4%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=3%2Ax%2B12-%2812%2F4%29%2Ax=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B12-%2812%2F4%29%2Ax=12\"   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=3%2Ax%2B12-3%2Ax=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B12-3%2Ax=12\"   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=3%2Ax-3%2Ax=12-12 ALIGN=MIDDLE  ALT=\"3%2Ax-3%2Ax=12-12\"   DISABLED_style= \"max-width:90%; height:auto;\" > Subtract <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12 ALIGN=MIDDLE  ALT=\"12\"   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=3%2Ax-3%2Ax=0 ALIGN=MIDDLE  ALT=\"3%2Ax-3%2Ax=0\"   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=0 ALIGN=MIDDLE  ALT=\"0%2Ax=0\"   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=0 ALIGN=MIDDLE  ALT=\"0=0\"   DISABLED_style= \"max-width:90%; height:auto;\" > Since this expression is true for any x, we have an identity. <BR>\n" );
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document.write( "  So there are an infinite number solutions. The simple reason is the 2 equations represent 2 lines that overlap each other. So they intersect each other at an infinite number of points.<BR>\n" );
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document.write( "  If we graph <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2Ax%2B4%2Ay=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B4%2Ay=12\"   DISABLED_style= \"max-width:90%; height:auto;\" > and <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2Ax%2B4%2Ay=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B4%2Ay=12\"   DISABLED_style= \"max-width:90%; height:auto;\" > we get <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+%2812-3%2Ax%29%2F4%29+ ALIGN=MIDDLE  ALT=\"+graph%28+500%2C+600%2C+-6%2C+5%2C+-10%2C+10%2C+%2812-3%2Ax%29%2F4%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > graph of <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2Ax%2B4%2Ay=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B4%2Ay=12\"   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=+graph%28+500%2C+600%2C+-6%2C+5%2C+-10%2C+10%2C+%2812-3%2Ax%29%2F4+%29+ ALIGN=MIDDLE  ALT=\"+graph%28+500%2C+600%2C+-6%2C+5%2C+-10%2C+10%2C+%2812-3%2Ax%29%2F4+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > graph of <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2Ax%2B4%2Ay=12 ALIGN=MIDDLE  ALT=\"3%2Ax%2B4%2Ay=12\"   DISABLED_style= \"max-width:90%; height:auto;\" > (hint: you may have to solve for y to graph these)<BR>\n" );
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document.write( "  we can see that these two lines are the same. So this system is <a  rel=nofollow HREF=http://www.algebra.com/algebra/homework/coordinate/lessons/Types-of-systems-inconsistent-dependent-independent.lesson>dependent</a></TD></TR>\n" );
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