document.write( "Question 688008: use the method of substitution to solve the system of linear equations\r
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Algebra.Com's Answer #425468 by MathLover1(20849)\"\" \"About 
You can put this solution on YOUR website!
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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( " \"2%2Ax-1%2Ay=8\"
\n" ); document.write( " \"9%2Ax-4%2Ay=37\"
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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=8-2%2Ax\"Subtract \"2%2Ax\" from both sides
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\n" ); document.write( " \"y=%288-2%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=-8%2B2%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"-8%2B2%2Ax\" we can substitute the expression \"-8%2B2%2Ax\" into y of the 2nd equation. This will eliminate y so we can solve for x.
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\n" ); document.write( " \"9%2Ax%2B-4%2Ahighlight%28%28-8%2B2%2Ax%29%29=37\" Replace y with \"-8%2B2%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"9%2Ax-4%2A%28-8%29-4%282%29x=37\" Distribute -4 to \"-8%2B2%2Ax\"
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\n" ); document.write( " \"9%2Ax%2B32-8%2Ax=37\" Multiply
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\n" ); document.write( " \"9%2Ax%2B32-8%2Ax=37\" Reduce any fractions
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\n" ); document.write( " \"9%2Ax-8%2Ax=37-32\" Subtract \"32\" from both sides
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\n" ); document.write( " \"9%2Ax-8%2Ax=5\" Combine the terms on the right side
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\n" ); document.write( " \"1%2Ax=5\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F1%29%281%2F1%29%29x=%285%2F1%29%281%2F1%29\" Multiply both sides by \"1%2F1\". This will cancel out \"1%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"5%2F1\" and \"1%2F1\" (and simplify) we get
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\n" ); document.write( " \"x=5\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=5\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"9%285%29-4%2Ay=37\" Plug in \"x=5\" into the 2nd equation
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\n" ); document.write( " \"45-4%2Ay=37\" Multiply
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\n" ); document.write( " \"-4%2Ay=37-45\"Subtract \"45\" from both sides
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\n" ); document.write( " \"-4%2Ay=-8\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F-4%29%28-4%29%29%2Ay=%28-8%2F1%29%281%2F-4%29\" Multiply both sides by \"1%2F-4\". This will cancel out -4 on the left side.
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\n" ); document.write( " \"y=-8%2F-4\" Multiply the terms on the right side
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\n" ); document.write( " \"y=2\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=2\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=5\" and \"y=2\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"5\",\"2\")
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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( " \"2%2Ax-1%2Ay=8\"
\n" ); document.write( " \"9%2Ax-4%2Ay=37\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"2%2Ax-1%2Ay=8\" (red) and \"9%2Ax-4%2Ay=37\" (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 (\"5\",\"2\"). This verifies our answer.
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\n" ); document.write( " Plug in (\"5\",\"2\") into the system of equations
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\n" ); document.write( " Let \"x=5\" and \"y=2\". Now plug those values into the equation \"2%2Ax-1%2Ay=8\"
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\n" ); document.write( " \"2%2A%285%29-1%2A%282%29=8\" Plug in \"x=5\" and \"y=2\"
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\n" ); document.write( " \"10-2=8\" Multiply
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\n" ); document.write( " \"8=8\" Add
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\n" ); document.write( " \"8=8\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"5\",\"2\") satisfies \"2%2Ax-1%2Ay=8\"
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\n" ); document.write( " Let \"x=5\" and \"y=2\". Now plug those values into the equation \"9%2Ax-4%2Ay=37\"
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\n" ); document.write( " \"9%2A%285%29-4%2A%282%29=37\" Plug in \"x=5\" and \"y=2\"
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\n" ); document.write( " \"45-8=37\" Multiply
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\n" ); document.write( " \"37=37\" Add
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\n" ); document.write( " \"37=37\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"5\",\"2\") satisfies \"9%2Ax-4%2Ay=37\"
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\n" ); document.write( " Since the solution (\"5\",\"2\") satisfies the system of equations
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\n" ); document.write( " \"2%2Ax-1%2Ay=8\"
\n" ); document.write( " \"9%2Ax-4%2Ay=37\"
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\n" ); document.write( " this verifies our answer.
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