document.write( "Question 99863: the sum of two numbers is 255. when the smaller number is subtracted from the larger, the result is -39.find the numbers \n" ); document.write( "
Algebra.Com's Answer #72686 by jim_thompson5910(35256)\"\" \"About 
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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%2B1%2Ay=255\"
\n" ); document.write( " \"1%2Ax-1%2Ay=-39\"
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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=255-1%2Ax\"Subtract \"1%2Ax\" from both sides
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\n" ); document.write( " \"y=%28255-1%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=255-1%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"255-1%2Ax\" we can substitute the expression \"255-1%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-1%2Ahighlight%28%28255-1%2Ax%29%29=-39\" Replace y with \"255-1%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"1%2Ax-1%2A%28255%29-1%28-1%29x=-39\" Distribute -1 to \"255-1%2Ax\"
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\n" ); document.write( " \"1%2Ax-255%2B1%2Ax=-39\" Multiply
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\n" ); document.write( " \"1%2Ax-255%2B1%2Ax=-39\" Reduce any fractions
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\n" ); document.write( " \"1%2Ax%2B1%2Ax=-39%2B255\"Add \"255\" to both sides
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\n" ); document.write( " \"1%2Ax%2B1%2Ax=216\" Combine the terms on the right side
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\n" ); document.write( " \"2%2Ax=216\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F2%29%282%2F1%29%29x=%28216%2F1%29%281%2F2%29\" Multiply both sides by \"1%2F2\". This will cancel out \"2%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"216%2F1\" and \"1%2F2\" (and simplify) we get
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\n" ); document.write( " \"x=108\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=108\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"1%28108%29-1%2Ay=-39\" Plug in \"x=108\" into the 2nd equation
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\n" ); document.write( " \"108-1%2Ay=-39\" Multiply
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\n" ); document.write( " \"-1%2Ay=-39-108\"Subtract \"108\" from both sides
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\n" ); document.write( " \"-1%2Ay=-147\" 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=%28-147%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=-147%2F-1\" Multiply the terms on the right side
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\n" ); document.write( " \"y=147\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=147\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=108\" and \"y=147\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"108\",\"147\")
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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%2B1%2Ay=255\"
\n" ); document.write( " \"1%2Ax-1%2Ay=-39\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"1%2Ax%2B1%2Ay=255\" (red) and \"1%2Ax-1%2Ay=-39\" (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 (\"108\",\"147\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"108\",\"147\") into the system of equations
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\n" ); document.write( " Let \"x=108\" and \"y=147\". Now plug those values into the equation \"1%2Ax%2B1%2Ay=255\"
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\n" ); document.write( " \"1%2A%28108%29%2B1%2A%28147%29=255\" Plug in \"x=108\" and \"y=147\"
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\n" ); document.write( " \"108%2B147=255\" Multiply
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\n" ); document.write( " \"255=255\" Add
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\n" ); document.write( " \"255=255\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"108\",\"147\") satisfies \"1%2Ax%2B1%2Ay=255\"
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\n" ); document.write( " Let \"x=108\" and \"y=147\". Now plug those values into the equation \"1%2Ax-1%2Ay=-39\"
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\n" ); document.write( " \"1%2A%28108%29-1%2A%28147%29=-39\" Plug in \"x=108\" and \"y=147\"
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\n" ); document.write( " \"108-147=-39\" Multiply
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\n" ); document.write( " \"-39=-39\" Add
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\n" ); document.write( " \"-39=-39\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"108\",\"147\") satisfies \"1%2Ax-1%2Ay=-39\"
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\n" ); document.write( " Since the solution (\"108\",\"147\") satisfies the system of equations
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\n" ); document.write( " \"1%2Ax%2B1%2Ay=255\"
\n" ); document.write( " \"1%2Ax-1%2Ay=-39\"
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\n" ); document.write( " this verifies our answer.
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\n" ); document.write( "\n" ); document.write( "So the two numbers are 108 and 147
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