document.write( "Question 89404: solve the system of equation by substitution
\n" ); document.write( "4x - 6y = 9
\n" ); document.write( "5x -6y =1
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Algebra.Com's Answer #64982 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( " \"4%2Ax-6%2Ay=9\"
\n" ); document.write( " \"5%2Ax-6%2Ay=1\"
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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( " \"-6%2Ay=9-4%2Ax\"Subtract \"4%2Ax\" from both sides
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\n" ); document.write( " \"y=%289-4%2Ax%29%2F-6\" Divide both sides by -6.
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\n" ); document.write( " Which breaks down and reduces to
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\n" ); document.write( " \"y=-3%2F2%2B%282%2F3%29%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"-3%2F2%2B%282%2F3%29%2Ax\" we can substitute the expression \"-3%2F2%2B%282%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( " \"5%2Ax%2B-6%2Ahighlight%28%28-3%2F2%2B%282%2F3%29%2Ax%29%29=1\" Replace y with \"-3%2F2%2B%282%2F3%29%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"5%2Ax-6%2A%28-3%2F2%29-6%282%2F3%29x=1\" Distribute -6 to \"-3%2F2%2B%282%2F3%29%2Ax\"
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\n" ); document.write( " \"5%2Ax%2B18%2F2-%2812%2F3%29%2Ax=1\" Multiply
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\n" ); document.write( " \"5%2Ax%2B9-4%2Ax=1\" Reduce any fractions
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\n" ); document.write( " \"5%2Ax-4%2Ax=1-9\" Subtract \"9\" from both sides
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\n" ); document.write( " \"5%2Ax-4%2Ax=-8\" Combine the terms on the right side
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\n" ); document.write( " \"1%2Ax=-8\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F1%29%281%2F1%29%29x=%28-8%2F1%29%281%2F1%29\" Multiply both sides by \"1%2F1\". This will cancel out \"1%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"-8%2F1\" and \"1%2F1\" (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( " \"5%28-8%29-6%2Ay=1\" Plug in \"x=-8\" into the 2nd equation
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\n" ); document.write( " \"-40-6%2Ay=1\" Multiply
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\n" ); document.write( " \"-6%2Ay=1%2B40\"Add \"40\" to both sides
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\n" ); document.write( " \"-6%2Ay=41\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F-6%29%28-6%29%29%2Ay=%2841%2F1%29%281%2F-6%29\" Multiply both sides by \"1%2F-6\". This will cancel out -6 on the left side.
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\n" ); document.write( " \"y=41%2F-6\" Multiply the terms on the right side
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\n" ); document.write( " \"y=-41%2F6\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=-41%2F6\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=-8\" and \"y=-41%2F6\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"-8\",\"-41%2F6\")
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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( " \"4%2Ax-6%2Ay=9\"
\n" ); document.write( " \"5%2Ax-6%2Ay=1\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"4%2Ax-6%2Ay=9\" (red) and \"5%2Ax-6%2Ay=1\" (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\",\"-41%2F6\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"-8\",\"-41%2F6\") into the system of equations
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\n" ); document.write( " Let \"x=-8\" and \"y=-41%2F6\". Now plug those values into the equation \"4%2Ax-6%2Ay=9\"
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\n" ); document.write( " \"4%2A%28-8%29-6%2A%28-41%2F6%29=9\" Plug in \"x=-8\" and \"y=-41%2F6\"
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\n" ); document.write( " \"-32%2B246%2F6=9\" Multiply
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\n" ); document.write( " \"54%2F6=9\" Add
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\n" ); document.write( " \"9=9\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"-8\",\"-41%2F6\") satisfies \"4%2Ax-6%2Ay=9\"
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\n" ); document.write( " Let \"x=-8\" and \"y=-41%2F6\". Now plug those values into the equation \"5%2Ax-6%2Ay=1\"
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\n" ); document.write( " \"5%2A%28-8%29-6%2A%28-41%2F6%29=1\" Plug in \"x=-8\" and \"y=-41%2F6\"
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\n" ); document.write( " \"-40%2B246%2F6=1\" Multiply
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\n" ); document.write( " \"6%2F6=1\" Add
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\n" ); document.write( " \"1=1\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"-8\",\"-41%2F6\") satisfies \"5%2Ax-6%2Ay=1\"
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\n" ); document.write( " Since the solution (\"-8\",\"-41%2F6\") satisfies the system of equations
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\n" ); document.write( " \"4%2Ax-6%2Ay=9\"
\n" ); document.write( " \"5%2Ax-6%2Ay=1\"
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\n" ); document.write( " this verifies our answer.
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