document.write( "Question 99569This question is from textbook Fundamentals of Algebraic Modeling
\n" ); document.write( ": I have not been able to figure out how to do the following problem.
\n" ); document.write( "x + 3y =2
\n" ); document.write( "x - 2y =-3
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Algebra.Com's Answer #72419 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%2B3%2Ay=2\"
\n" ); document.write( " \"1%2Ax-2%2Ay=-3\"
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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( " \"3%2Ay=2-1%2Ax\"Subtract \"1%2Ax\" from both sides
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\n" ); document.write( " \"y=%282-1%2Ax%29%2F3\" Divide both sides by 3.
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\n" ); document.write( " Which breaks down and reduces to
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\n" ); document.write( " \"y=2%2F3-%281%2F3%29%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"2%2F3-%281%2F3%29%2Ax\" we can substitute the expression \"2%2F3-%281%2F3%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( " \"1%2Ax%2B-2%2Ahighlight%28%282%2F3-%281%2F3%29%2Ax%29%29=-3\" Replace y with \"2%2F3-%281%2F3%29%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"1%2Ax-2%2A%282%2F3%29-2%28-1%2F3%29x=-3\" Distribute -2 to \"2%2F3-%281%2F3%29%2Ax\"
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\n" ); document.write( " \"1%2Ax-4%2F3%2B%282%2F3%29%2Ax=-3\" Multiply
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\n" ); document.write( " \"1%2Ax-4%2F3%2B%282%2F3%29%2Ax=-3\" Reduce any fractions
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\n" ); document.write( " \"1%2Ax%2B%282%2F3%29%2Ax=-3%2B4%2F3\"Add \"4%2F3\" to both sides
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\n" ); document.write( " \"1%2Ax%2B%282%2F3%29%2Ax=-9%2F3%2B4%2F3\" Make -3 into a fraction with a denominator of 3
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\n" ); document.write( " \"1%2Ax%2B%282%2F3%29%2Ax=-5%2F3\" Combine the terms on the right side
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\n" ); document.write( " \"%283%2F3%29%2Ax%2B%282%2F3%29x=-5%2F3\" Make 1 into a fraction with a denominator of 3
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\n" ); document.write( " \"%285%2F3%29%2Ax=-5%2F3\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%283%2F5%29%285%2F3%29%29x=%28-5%2F3%29%283%2F5%29\" Multiply both sides by \"3%2F5\". This will cancel out \"5%2F3\" and isolate x
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\n" ); document.write( " So when we multiply \"-5%2F3\" and \"3%2F5\" (and simplify) we get
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\n" ); document.write( " \"x=-1\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=-1\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"1%28-1%29-2%2Ay=-3\" Plug in \"x=-1\" into the 2nd equation
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\n" ); document.write( " \"-1-2%2Ay=-3\" Multiply
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\n" ); document.write( " \"-2%2Ay=-3%2B1\"Add \"1\" to both sides
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\n" ); document.write( " \"-2%2Ay=-2\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F-2%29%28-2%29%29%2Ay=%28-2%2F1%29%281%2F-2%29\" Multiply both sides by \"1%2F-2\". This will cancel out -2 on the left side.
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\n" ); document.write( " \"y=-2%2F-2\" 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=-1\" and \"y=1\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"-1\",\"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%2B3%2Ay=2\"
\n" ); document.write( " \"1%2Ax-2%2Ay=-3\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"1%2Ax%2B3%2Ay=2\" (red) and \"1%2Ax-2%2Ay=-3\" (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 (\"-1\",\"1\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"-1\",\"1\") into the system of equations
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\n" ); document.write( " Let \"x=-1\" and \"y=1\". Now plug those values into the equation \"1%2Ax%2B3%2Ay=2\"
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\n" ); document.write( " \"1%2A%28-1%29%2B3%2A%281%29=2\" Plug in \"x=-1\" and \"y=1\"
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\n" ); document.write( " \"-1%2B3=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 (\"-1\",\"1\") satisfies \"1%2Ax%2B3%2Ay=2\"
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\n" ); document.write( " Let \"x=-1\" and \"y=1\". Now plug those values into the equation \"1%2Ax-2%2Ay=-3\"
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\n" ); document.write( " \"1%2A%28-1%29-2%2A%281%29=-3\" Plug in \"x=-1\" and \"y=1\"
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\n" ); document.write( " \"-1-2=-3\" Multiply
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\n" ); document.write( " \"-3=-3\" Add
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\n" ); document.write( " \"-3=-3\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"-1\",\"1\") satisfies \"1%2Ax-2%2Ay=-3\"
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\n" ); document.write( " Since the solution (\"-1\",\"1\") satisfies the system of equations
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\n" ); document.write( " \"1%2Ax%2B3%2Ay=2\"
\n" ); document.write( " \"1%2Ax-2%2Ay=-3\"
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\n" ); document.write( " this verifies our answer.
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