document.write( "Question 120684: please help me sove this problem
\n" ); document.write( "use the substitution method to solve the linear system
\n" ); document.write( "here is the promblem
\n" ); document.write( "m-5n=18
\n" ); document.write( "2m-3m=-13
\n" ); document.write( "please help
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Algebra.Com's Answer #88469 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
note: I'm going to use x and y instead of m and n\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( " \"1%2Ax-5%2Ay=18\"
\n" ); document.write( " \"2%2Ax-3%2Ay=-13\"
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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=18-1%2Ax\"Subtract \"1%2Ax\" from both sides
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\n" ); document.write( " \"y=%2818-1%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=-18%2F5%2B%281%2F5%29%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"-18%2F5%2B%281%2F5%29%2Ax\" we can substitute the expression \"-18%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%2B-3%2Ahighlight%28%28-18%2F5%2B%281%2F5%29%2Ax%29%29=-13\" Replace y with \"-18%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-3%2A%28-18%2F5%29-3%281%2F5%29x=-13\" Distribute -3 to \"-18%2F5%2B%281%2F5%29%2Ax\"
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\n" ); document.write( " \"2%2Ax%2B54%2F5-%283%2F5%29%2Ax=-13\" Multiply
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\n" ); document.write( " \"2%2Ax%2B54%2F5-%283%2F5%29%2Ax=-13\" Reduce any fractions
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\n" ); document.write( " \"2%2Ax-%283%2F5%29%2Ax=-13-54%2F5\" Subtract \"54%2F5\" from both sides
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\n" ); document.write( " \"2%2Ax-%283%2F5%29%2Ax=-65%2F5-54%2F5\" Make -13 into a fraction with a denominator of 5
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\n" ); document.write( " \"2%2Ax-%283%2F5%29%2Ax=-119%2F5\" Combine the terms on the right side
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\n" ); document.write( " \"%2810%2F5%29%2Ax-%283%2F5%29x=-119%2F5\" Make 2 into a fraction with a denominator of 5
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\n" ); document.write( " \"%287%2F5%29%2Ax=-119%2F5\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%285%2F7%29%287%2F5%29%29x=%28-119%2F5%29%285%2F7%29\" Multiply both sides by \"5%2F7\". This will cancel out \"7%2F5\" and isolate x
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\n" ); document.write( " So when we multiply \"-119%2F5\" and \"5%2F7\" (and simplify) we get
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\n" ); document.write( " \"x=-17\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=-17\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"2%28-17%29-3%2Ay=-13\" Plug in \"x=-17\" into the 2nd equation
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\n" ); document.write( " \"-34-3%2Ay=-13\" Multiply
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\n" ); document.write( " \"-3%2Ay=-13%2B34\"Add \"34\" to both sides
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\n" ); document.write( " \"-3%2Ay=21\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F-3%29%28-3%29%29%2Ay=%2821%2F1%29%281%2F-3%29\" Multiply both sides by \"1%2F-3\". This will cancel out -3 on the left side.
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\n" ); document.write( " \"y=21%2F-3\" Multiply the terms on the right side
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\n" ); document.write( " \"y=-7\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=-7\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=-17\" and \"y=-7\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"-17\",\"-7\")
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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=18\"
\n" ); document.write( " \"2%2Ax-3%2Ay=-13\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"1%2Ax-5%2Ay=18\" (red) and \"2%2Ax-3%2Ay=-13\" (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 (\"-17\",\"-7\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"-17\",\"-7\") into the system of equations
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\n" ); document.write( " Let \"x=-17\" and \"y=-7\". Now plug those values into the equation \"1%2Ax-5%2Ay=18\"
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\n" ); document.write( " \"1%2A%28-17%29-5%2A%28-7%29=18\" Plug in \"x=-17\" and \"y=-7\"
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\n" ); document.write( " \"-17%2B35=18\" Multiply
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\n" ); document.write( " \"18=18\" Add
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\n" ); document.write( " \"18=18\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"-17\",\"-7\") satisfies \"1%2Ax-5%2Ay=18\"
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\n" ); document.write( " Let \"x=-17\" and \"y=-7\". Now plug those values into the equation \"2%2Ax-3%2Ay=-13\"
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\n" ); document.write( " \"2%2A%28-17%29-3%2A%28-7%29=-13\" Plug in \"x=-17\" and \"y=-7\"
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\n" ); document.write( " \"-34%2B21=-13\" Multiply
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\n" ); document.write( " \"-13=-13\" Add
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\n" ); document.write( " \"-13=-13\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"-17\",\"-7\") satisfies \"2%2Ax-3%2Ay=-13\"
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\n" ); document.write( " Since the solution (\"-17\",\"-7\") satisfies the system of equations
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\n" ); document.write( " \"1%2Ax-5%2Ay=18\"
\n" ); document.write( " \"2%2Ax-3%2Ay=-13\"
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\n" ); document.write( " this verifies our answer.
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