document.write( "Question 178131: sorry i posted the wrong equation, here are the right ones\r
\n" ); document.write( "\n" ); document.write( "2x + y = 7\r
\n" ); document.write( "\n" ); document.write( "x + 5y = 12
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Algebra.Com's Answer #133067 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Let's solve the system by using substitution:\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( " \"2%2Ax%2B1%2Ay=7\"
\n" ); document.write( " \"1%2Ax%2B5%2Ay=12\"
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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=7-2%2Ax\"Subtract \"2%2Ax\" from both sides
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\n" ); document.write( " \"y=%287-2%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=7-2%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"7-2%2Ax\" we can substitute the expression \"7-2%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%2B5%2Ahighlight%28%287-2%2Ax%29%29=12\" Replace y with \"7-2%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"1%2Ax%2B5%2A%287%29%2B5%28-2%29x=12\" Distribute 5 to \"7-2%2Ax\"
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\n" ); document.write( " \"1%2Ax%2B35-10%2Ax=12\" Multiply
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\n" ); document.write( " \"1%2Ax%2B35-10%2Ax=12\" Reduce any fractions
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\n" ); document.write( " \"1%2Ax-10%2Ax=12-35\" Subtract \"35\" from both sides
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\n" ); document.write( " \"1%2Ax-10%2Ax=-23\" Combine the terms on the right side
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\n" ); document.write( " \"-9%2Ax=-23\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F-9%29%28-9%2F1%29%29x=%28-23%2F1%29%281%2F-9%29\" Multiply both sides by \"1%2F-9\". This will cancel out \"-9%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"-23%2F1\" and \"1%2F-9\" (and simplify) we get
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\n" ); document.write( " \"x=23%2F9\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=23%2F9\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"1%2823%2F9%29%2B5%2Ay=12\" Plug in \"x=23%2F9\" into the 2nd equation
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\n" ); document.write( " \"23%2F9%2B5%2Ay=12\" Multiply
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\n" ); document.write( " \"5%2Ay=12-23%2F9\"Subtract \"23%2F9\" from both sides
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\n" ); document.write( " \"5%2Ay=108%2F9-23%2F9\" Make 12 into a fraction with a denominator of 9
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\n" ); document.write( " \"5%2Ay=85%2F9\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F5%29%285%29%29%2Ay=%2885%2F9%29%281%2F5%29\" Multiply both sides by \"1%2F5\". This will cancel out 5 on the left side.
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\n" ); document.write( " \"y=85%2F45\" Multiply the terms on the right side
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\n" ); document.write( " \"y=17%2F9\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=17%2F9\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=23%2F9\" and \"y=17%2F9\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"23%2F9\",\"17%2F9\")
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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%2B1%2Ay=7\"
\n" ); document.write( " \"1%2Ax%2B5%2Ay=12\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"2%2Ax%2B1%2Ay=7\" (red) and \"1%2Ax%2B5%2Ay=12\" (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 (\"23%2F9\",\"17%2F9\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"23%2F9\",\"17%2F9\") into the system of equations
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\n" ); document.write( " Let \"x=23%2F9\" and \"y=17%2F9\". Now plug those values into the equation \"2%2Ax%2B1%2Ay=7\"
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\n" ); document.write( " \"2%2A%2823%2F9%29%2B1%2A%2817%2F9%29=7\" Plug in \"x=23%2F9\" and \"y=17%2F9\"
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\n" ); document.write( " \"46%2F9%2B17%2F9=7\" Multiply
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\n" ); document.write( " \"63%2F9=7\" Add
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\n" ); document.write( " \"7=7\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"23%2F9\",\"17%2F9\") satisfies \"2%2Ax%2B1%2Ay=7\"
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\n" ); document.write( " Let \"x=23%2F9\" and \"y=17%2F9\". Now plug those values into the equation \"1%2Ax%2B5%2Ay=12\"
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\n" ); document.write( " \"1%2A%2823%2F9%29%2B5%2A%2817%2F9%29=12\" Plug in \"x=23%2F9\" and \"y=17%2F9\"
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\n" ); document.write( " \"23%2F9%2B85%2F9=12\" Multiply
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\n" ); document.write( " \"108%2F9=12\" Add
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\n" ); document.write( " \"12=12\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"23%2F9\",\"17%2F9\") satisfies \"1%2Ax%2B5%2Ay=12\"
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\n" ); document.write( " Since the solution (\"23%2F9\",\"17%2F9\") satisfies the system of equations
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\n" ); document.write( " \"2%2Ax%2B1%2Ay=7\"
\n" ); document.write( " \"1%2Ax%2B5%2Ay=12\"
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\n" ); document.write( " this verifies our answer.
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