document.write( "Question 120287: Solve each system of equations. check by substitution\r
\n" ); document.write( "\n" ); document.write( "4m + n = 17
\n" ); document.write( "3m - 4n = 27
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Algebra.Com's Answer #88160 by MathLover1(20849)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "\"4m+%2B+n+=+17\"
\n" ); document.write( "\"3m+-+4n+=+27\"\r
\n" ); document.write( "\n" ); document.write( "let \"m=x\" and \"n=y\"\r
\n" ); document.write( "\n" ); document.write( "solution:\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%2B1%2Ay=17\"
\n" ); document.write( " \"3%2Ax-4%2Ay=27\"
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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=17-4%2Ax\"Subtract \"4%2Ax\" from both sides
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\n" ); document.write( " \"y=%2817-4%2Ax%29\" 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=17-4%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"17-4%2Ax\" we can substitute the expression \"17-4%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-4%2Ahighlight%28%2817-4%2Ax%29%29=27\" Replace y with \"17-4%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"3%2Ax-4%2A%2817%29-4%28-4%29x=27\" Distribute -4 to \"17-4%2Ax\"
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\n" ); document.write( " \"3%2Ax-68%2B16%2Ax=27\" Multiply
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\n" ); document.write( " \"3%2Ax-68%2B16%2Ax=27\" Reduce any fractions
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\n" ); document.write( " \"3%2Ax%2B16%2Ax=27%2B68\"Add \"68\" to both sides
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\n" ); document.write( " \"3%2Ax%2B16%2Ax=95\" Combine the terms on the right side
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\n" ); document.write( " \"19%2Ax=95\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F19%29%2819%2F1%29%29x=%2895%2F1%29%281%2F19%29\" Multiply both sides by \"1%2F19\". This will cancel out \"19%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"95%2F1\" and \"1%2F19\" (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( " \"3%285%29-4%2Ay=27\" Plug in \"x=5\" into the 2nd equation
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\n" ); document.write( " \"15-4%2Ay=27\" Multiply
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\n" ); document.write( " \"-4%2Ay=27-15\"Subtract \"15\" from both sides
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\n" ); document.write( " \"-4%2Ay=12\" 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=%2812%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=12%2F-4\" Multiply the terms on the right side
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\n" ); document.write( " \"y=-3\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=-3\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=5\" and \"y=-3\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"5\",\"-3\")
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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%2B1%2Ay=17\"
\n" ); document.write( " \"3%2Ax-4%2Ay=27\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"4%2Ax%2B1%2Ay=17\" (red) and \"3%2Ax-4%2Ay=27\" (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\",\"-3\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"5\",\"-3\") into the system of equations
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\n" ); document.write( " Let \"x=5\" and \"y=-3\". Now plug those values into the equation \"4%2Ax%2B1%2Ay=17\"
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\n" ); document.write( " \"4%2A%285%29%2B1%2A%28-3%29=17\" Plug in \"x=5\" and \"y=-3\"
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\n" ); document.write( " \"20-3=17\" Multiply
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\n" ); document.write( " \"17=17\" Add
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\n" ); document.write( " \"17=17\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"5\",\"-3\") satisfies \"4%2Ax%2B1%2Ay=17\"
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\n" ); document.write( " Let \"x=5\" and \"y=-3\". Now plug those values into the equation \"3%2Ax-4%2Ay=27\"
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\n" ); document.write( " \"3%2A%285%29-4%2A%28-3%29=27\" Plug in \"x=5\" and \"y=-3\"
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\n" ); document.write( " \"15%2B12=27\" Multiply
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\n" ); document.write( " \"27=27\" Add
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\n" ); document.write( " \"27=27\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"5\",\"-3\") satisfies \"3%2Ax-4%2Ay=27\"
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\n" ); document.write( " Since the solution (\"5\",\"-3\") satisfies the system of equations
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\n" ); document.write( " \"4%2Ax%2B1%2Ay=17\"
\n" ); document.write( " \"3%2Ax-4%2Ay=27\"
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\n" ); document.write( " this verifies our answer.
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