document.write( "Question 110529: solve the system by substitution.\r
\n" ); document.write( "\n" ); document.write( "x - 5y = 2\r
\n" ); document.write( "\n" ); document.write( "2x + 3y = 17
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Algebra.Com's Answer #80792 by jim_thompson5910(35256)\"\" \"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( " \"1%2Ax-5%2Ay=2\"
\n" ); document.write( " \"2%2Ax%2B3%2Ay=17\"
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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( " \"-5%2Ay=2-1%2Ax\"Subtract \"1%2Ax\" from both sides
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\n" ); document.write( " \"y=%282-1%2Ax%29%2F-5\" Divide both sides by -5.
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\n" ); document.write( " Which breaks down and reduces to
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\n" ); document.write( " \"y=-2%2F5%2B%281%2F5%29%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"-2%2F5%2B%281%2F5%29%2Ax\" we can substitute the expression \"-2%2F5%2B%281%2F5%29%2Ax\" into y of the 2nd equation. This will eliminate y so we can solve for x.
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\n" ); document.write( " \"2%2Ax%2B3%2Ahighlight%28%28-2%2F5%2B%281%2F5%29%2Ax%29%29=17\" Replace y with \"-2%2F5%2B%281%2F5%29%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"2%2Ax%2B3%2A%28-2%2F5%29%2B3%281%2F5%29x=17\" Distribute 3 to \"-2%2F5%2B%281%2F5%29%2Ax\"
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\n" ); document.write( " \"2%2Ax-6%2F5%2B%283%2F5%29%2Ax=17\" Multiply
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\n" ); document.write( " \"2%2Ax-6%2F5%2B%283%2F5%29%2Ax=17\" Reduce any fractions
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\n" ); document.write( " \"2%2Ax%2B%283%2F5%29%2Ax=17%2B6%2F5\"Add \"6%2F5\" to both sides
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\n" ); document.write( " \"2%2Ax%2B%283%2F5%29%2Ax=85%2F5%2B6%2F5\" Make 17 into a fraction with a denominator of 5
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\n" ); document.write( " \"2%2Ax%2B%283%2F5%29%2Ax=91%2F5\" Combine the terms on the right side
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\n" ); document.write( " \"%2810%2F5%29%2Ax%2B%283%2F5%29x=91%2F5\" Make 2 into a fraction with a denominator of 5
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\n" ); document.write( " \"%2813%2F5%29%2Ax=91%2F5\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%285%2F13%29%2813%2F5%29%29x=%2891%2F5%29%285%2F13%29\" Multiply both sides by \"5%2F13\". This will cancel out \"13%2F5\" and isolate x
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\n" ); document.write( " So when we multiply \"91%2F5\" and \"5%2F13\" (and simplify) we get
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\n" ); document.write( " \"x=7\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=7\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"2%287%29%2B3%2Ay=17\" Plug in \"x=7\" into the 2nd equation
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\n" ); document.write( " \"14%2B3%2Ay=17\" Multiply
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\n" ); document.write( " \"3%2Ay=17-14\"Subtract \"14\" from both sides
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\n" ); document.write( " \"3%2Ay=3\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F3%29%283%29%29%2Ay=%283%2F1%29%281%2F3%29\" Multiply both sides by \"1%2F3\". This will cancel out 3 on the left side.
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\n" ); document.write( " \"y=3%2F3\" Multiply the terms on the right side
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\n" ); document.write( " \"y=1\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=1\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=7\" and \"y=1\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"7\",\"1\")
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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-5%2Ay=2\"
\n" ); document.write( " \"2%2Ax%2B3%2Ay=17\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"1%2Ax-5%2Ay=2\" (red) and \"2%2Ax%2B3%2Ay=17\" (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 (\"7\",\"1\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"7\",\"1\") into the system of equations
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\n" ); document.write( " Let \"x=7\" and \"y=1\". Now plug those values into the equation \"1%2Ax-5%2Ay=2\"
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\n" ); document.write( " \"1%2A%287%29-5%2A%281%29=2\" Plug in \"x=7\" and \"y=1\"
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\n" ); document.write( " \"7-5=2\" Multiply
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\n" ); document.write( " \"2=2\" Add
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\n" ); document.write( " \"2=2\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"7\",\"1\") satisfies \"1%2Ax-5%2Ay=2\"
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\n" ); document.write( " Let \"x=7\" and \"y=1\". Now plug those values into the equation \"2%2Ax%2B3%2Ay=17\"
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\n" ); document.write( " \"2%2A%287%29%2B3%2A%281%29=17\" Plug in \"x=7\" and \"y=1\"
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\n" ); document.write( " \"14%2B3=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 (\"7\",\"1\") satisfies \"2%2Ax%2B3%2Ay=17\"
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\n" ); document.write( " Since the solution (\"7\",\"1\") satisfies the system of equations
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\n" ); document.write( " \"1%2Ax-5%2Ay=2\"
\n" ); document.write( " \"2%2Ax%2B3%2Ay=17\"
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\n" ); document.write( " this verifies our answer.
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