document.write( "Question 948990: Please help me solve this system of equations \r
\n" ); document.write( "\n" ); document.write( "X=y-11 and x-3y=1
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Algebra.Com's Answer #579281 by MathLover1(20850)\"\" \"About 
You can put this solution on YOUR website!
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\n" ); document.write( "\"x-3y=1\"
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\n" ); document.write( "\n" ); document.write( "\"x-y=-11\"
\n" ); document.write( "\"x-3y=1\"\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( " \"1%2Ax-1%2Ay=-11\"
\n" ); document.write( " \"1%2Ax-3%2Ay=1\"
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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( " \"-1%2Ay=-11-1%2Ax\"Subtract \"1%2Ax\" from both sides
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\n" ); document.write( " \"y=%28-11-1%2Ax%29%2F-1\" Divide both sides by -1.
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\n" ); document.write( " Which breaks down and reduces to
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\n" ); document.write( " \"y=11%2B1%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"11%2B1%2Ax\" we can substitute the expression \"11%2B1%2Ax\" into y of the 2nd equation. This will eliminate y so we can solve for x.
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\n" ); document.write( " \"1%2Ax%2B-3%2Ahighlight%28%2811%2B1%2Ax%29%29=1\" Replace y with \"11%2B1%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"1%2Ax-3%2A%2811%29-3%281%29x=1\" Distribute -3 to \"11%2B1%2Ax\"
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\n" ); document.write( " \"1%2Ax-33-3%2Ax=1\" Multiply
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\n" ); document.write( " \"1%2Ax-33-3%2Ax=1\" Reduce any fractions
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\n" ); document.write( " \"1%2Ax-3%2Ax=1%2B33\"Add \"33\" to both sides
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\n" ); document.write( " \"1%2Ax-3%2Ax=34\" Combine the terms on the right side
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\n" ); document.write( " \"-2%2Ax=34\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F-2%29%28-2%2F1%29%29x=%2834%2F1%29%281%2F-2%29\" Multiply both sides by \"1%2F-2\". This will cancel out \"-2%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"34%2F1\" and \"1%2F-2\" (and simplify) we get
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\n" ); document.write( " \"x=-17\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=-17\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"1%28-17%29-3%2Ay=1\" Plug in \"x=-17\" into the 2nd equation
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\n" ); document.write( " \"-17-3%2Ay=1\" Multiply
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\n" ); document.write( " \"-3%2Ay=1%2B17\"Add \"17\" to both sides
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\n" ); document.write( " \"-3%2Ay=18\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F-3%29%28-3%29%29%2Ay=%2818%2F1%29%281%2F-3%29\" Multiply both sides by \"1%2F-3\". This will cancel out -3 on the left side.
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\n" ); document.write( " \"y=18%2F-3\" Multiply the terms on the right side
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\n" ); document.write( " \"y=-6\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=-6\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=-17\" and \"y=-6\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"-17\",\"-6\")
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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( " \"1%2Ax-1%2Ay=-11\"
\n" ); document.write( " \"1%2Ax-3%2Ay=1\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"1%2Ax-1%2Ay=-11\" (red) and \"1%2Ax-3%2Ay=1\" (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 (\"-17\",\"-6\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"-17\",\"-6\") into the system of equations
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\n" ); document.write( " Let \"x=-17\" and \"y=-6\". Now plug those values into the equation \"1%2Ax-1%2Ay=-11\"
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\n" ); document.write( " \"1%2A%28-17%29-1%2A%28-6%29=-11\" Plug in \"x=-17\" and \"y=-6\"
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\n" ); document.write( " \"-17%2B6=-11\" Multiply
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\n" ); document.write( " \"-11=-11\" Add
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\n" ); document.write( " \"-11=-11\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"-17\",\"-6\") satisfies \"1%2Ax-1%2Ay=-11\"
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\n" ); document.write( " Let \"x=-17\" and \"y=-6\". Now plug those values into the equation \"1%2Ax-3%2Ay=1\"
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\n" ); document.write( " \"1%2A%28-17%29-3%2A%28-6%29=1\" Plug in \"x=-17\" and \"y=-6\"
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\n" ); document.write( " \"-17%2B18=1\" Multiply
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\n" ); document.write( " \"1=1\" Add
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\n" ); document.write( " \"1=1\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"-17\",\"-6\") satisfies \"1%2Ax-3%2Ay=1\"
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\n" ); document.write( " Since the solution (\"-17\",\"-6\") satisfies the system of equations
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\n" ); document.write( " \"1%2Ax-1%2Ay=-11\"
\n" ); document.write( " \"1%2Ax-3%2Ay=1\"
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\n" ); document.write( " this verifies our answer.
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