document.write( "Question 399717: how do i solve -4x-y=y and 3x-y=0 in subsitution form. \n" ); document.write( "
Algebra.Com's Answer #283040 by MathLover1(20850)\"\" \"About 
You can put this solution on YOUR website!
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\n" ); document.write( "\n" ); document.write( "\"-4x-y=y\" ...add \"-y\" to the both sides \r
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\n" ); document.write( "\n" ); document.write( "\"-4x-y+-y=y-y\"\r
\n" ); document.write( "\n" ); document.write( "\"-4x-2y+=+0\"\r
\n" ); document.write( "\n" ); document.write( "now solve in substitution form:\r
\n" ); document.write( "\n" ); document.write( "\"-4x-2y+=+0\"\r
\n" ); document.write( "\n" ); document.write( "\"3x-y=0+\"\r
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Solved by pluggable solver: Solving a linear system of equations by subsitution

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\n" ); document.write( " Lets start with the given system of linear equations
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\n" ); document.write( " \"-4%2Ax-2%2Ay=0\"
\n" ); document.write( " \"3%2Ax-1%2Ay=0\"
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\n" ); 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.
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\n" ); document.write( " Solve for y for the first equation
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\n" ); document.write( " \"-2%2Ay=0%2B4%2Ax\"Add \"4%2Ax\" to both sides
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\n" ); document.write( " \"y=%280%2B4%2Ax%29%2F-2\" Divide both sides by -2.
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\n" ); document.write( " Which breaks down and reduces to
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\n" ); document.write( " \"y=0-2%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"0-2%2Ax\" we can substitute the expression \"0-2%2Ax\" into y of the 2nd equation. This will eliminate y so we can solve for x.
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\n" ); document.write( " \"3%2Ax%2B-1%2Ahighlight%28%280-2%2Ax%29%29=0\" Replace y with \"0-2%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"3%2Ax-1%2A%280%29-1%28-2%29x=0\" Distribute -1 to \"0-2%2Ax\"
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\n" ); document.write( " \"3%2Ax%2B0%2B2%2Ax=0\" Multiply
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\n" ); document.write( " \"3%2Ax%2B0%2B2%2Ax=0\" Reduce any fractions
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\n" ); document.write( " \"3%2Ax%2B2%2Ax=0%2B0\"Add \"0\" to both sides
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\n" ); document.write( " \"3%2Ax%2B2%2Ax=0\" Combine the terms on the right side
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\n" ); document.write( " \"5%2Ax=0\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F5%29%285%2F1%29%29x=%280%2F1%29%281%2F5%29\" Multiply both sides by \"1%2F5\". This will cancel out \"5%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"0%2F1\" and \"1%2F5\" (and simplify) we get
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\n" ); document.write( " \"x=0\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=0\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"3%280%29-1%2Ay=0\" Plug in \"x=0\" into the 2nd equation
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\n" ); document.write( " \"0-1%2Ay=0\" Multiply
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\n" ); document.write( " \"-1%2Ay=0%2B0\"Add \"0\" to both sides
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\n" ); document.write( " \"-1%2Ay=0\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F-1%29%28-1%29%29%2Ay=%280%2F1%29%281%2F-1%29\" Multiply both sides by \"1%2F-1\". This will cancel out -1 on the left side.
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\n" ); document.write( " \"y=0%2F-1\" Multiply the terms on the right side
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\n" ); document.write( " \"y=0\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=0\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=0\" and \"y=0\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"0\",\"0\")
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\n" ); document.write( " Notice if we graph the equations (if you need help with graphing, check out this solver)
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\n" ); document.write( " \"-4%2Ax-2%2Ay=0\"
\n" ); document.write( " \"3%2Ax-1%2Ay=0\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"-4%2Ax-2%2Ay=0\" (red) and \"3%2Ax-1%2Ay=0\" (green) (hint: you may have to solve for y to graph these) intersecting at the blue circle.
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\n" ); document.write( " and we can see that the two equations intersect at (\"0\",\"0\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"0\",\"0\") into the system of equations
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\n" ); document.write( " Let \"x=0\" and \"y=0\". Now plug those values into the equation \"-4%2Ax-2%2Ay=0\"
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\n" ); document.write( " \"-4%2A%280%29-2%2A%280%29=0\" Plug in \"x=0\" and \"y=0\"
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\n" ); document.write( " \"0%2B0=0\" Multiply
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\n" ); document.write( " \"0=0\" Add
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\n" ); document.write( " \"0=0\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"0\",\"0\") satisfies \"-4%2Ax-2%2Ay=0\"
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\n" ); document.write( " Let \"x=0\" and \"y=0\". Now plug those values into the equation \"3%2Ax-1%2Ay=0\"
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\n" ); document.write( " \"3%2A%280%29-1%2A%280%29=0\" Plug in \"x=0\" and \"y=0\"
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\n" ); document.write( " \"0%2B0=0\" Multiply
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\n" ); document.write( " \"0=0\" Add
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\n" ); document.write( "
\n" ); document.write( " \"0=0\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"0\",\"0\") satisfies \"3%2Ax-1%2Ay=0\"
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\n" ); document.write( " Since the solution (\"0\",\"0\") satisfies the system of equations
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\n" ); document.write( " \"-4%2Ax-2%2Ay=0\"
\n" ); document.write( " \"3%2Ax-1%2Ay=0\"
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\n" ); document.write( " this verifies our answer.
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