document.write( "Question 88243: find two numbers of which the sum is 11 and the difference is 5. \n" ); document.write( "
Algebra.Com's Answer #64073 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=11\"
\n" ); document.write( " \"1%2Ax-1%2Ay=5\"
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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=%2811-1%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=11-1%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"11-1%2Ax\" we can substitute the expression \"11-1%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%2811-1%2Ax%29%29=5\" Replace y with \"11-1%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"1%2Ax-1%2A%2811%29-1%28-1%29x=5\" Distribute -1 to \"11-1%2Ax\"
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\n" ); document.write( " \"1%2Ax-11%2B1%2Ax=5\" Multiply
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\n" ); document.write( " \"1%2Ax-11%2B1%2Ax=5\" Reduce any fractions
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\n" ); document.write( " \"1%2Ax%2B1%2Ax=5%2B11\"Add \"11\" to both sides
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\n" ); document.write( " \"1%2Ax%2B1%2Ax=16\" Combine the terms on the right side
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\n" ); document.write( " \"2%2Ax=16\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F2%29%282%2F1%29%29x=%2816%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 \"16%2F1\" and \"1%2F2\" (and simplify) we get
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\n" ); document.write( " \"x=8\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=8\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"1%288%29-1%2Ay=5\" Plug in \"x=8\" into the 2nd equation
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\n" ); document.write( " \"8-1%2Ay=5\" Multiply
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\n" ); document.write( " \"-1%2Ay=5-8\"Subtract \"8\" from both sides
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\n" ); document.write( " \"-1%2Ay=-3\" 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=%28-3%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=-3%2F-1\" 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=8\" and \"y=3\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"8\",\"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( " \"1%2Ax%2B1%2Ay=11\"
\n" ); document.write( " \"1%2Ax-1%2Ay=5\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"1%2Ax%2B1%2Ay=11\" (red) and \"1%2Ax-1%2Ay=5\" (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 (\"8\",\"3\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"8\",\"3\") into the system of equations
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\n" ); document.write( " Let \"x=8\" and \"y=3\". Now plug those values into the equation \"1%2Ax%2B1%2Ay=11\"
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\n" ); document.write( " \"1%2A%288%29%2B1%2A%283%29=11\" Plug in \"x=8\" and \"y=3\"
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\n" ); document.write( " \"8%2B3=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 (\"8\",\"3\") satisfies \"1%2Ax%2B1%2Ay=11\"
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\n" ); document.write( " Let \"x=8\" and \"y=3\". Now plug those values into the equation \"1%2Ax-1%2Ay=5\"
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\n" ); document.write( " \"1%2A%288%29-1%2A%283%29=5\" Plug in \"x=8\" and \"y=3\"
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\n" ); document.write( " \"8-3=5\" Multiply
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\n" ); document.write( " \"5=5\" Add
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\n" ); document.write( " \"5=5\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"8\",\"3\") satisfies \"1%2Ax-1%2Ay=5\"
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\n" ); document.write( " Since the solution (\"8\",\"3\") satisfies the system of equations
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\n" ); document.write( " \"1%2Ax%2B1%2Ay=11\"
\n" ); document.write( " \"1%2Ax-1%2Ay=5\"
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\n" ); document.write( " this verifies our answer.
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\n" ); document.write( "\n" ); document.write( "So the 2 numbers are 8 and 3
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