document.write( "Question 142156: Solve by substitution or elimination and circle the method you have chosen.\r
\n" ); document.write( "\n" ); document.write( "(2x + 3y = -11
\n" ); document.write( "(4x - 2y = 2
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Algebra.Com's Answer #103578 by MathLover1(20850)\"\" \"About 
You can put this solution on YOUR website!
by 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%2B3%2Ay=-11\"
\n" ); document.write( " \"4%2Ax-2%2Ay=2\"
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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=-11-2%2Ax\"Subtract \"2%2Ax\" from both sides
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\n" ); document.write( " \"y=%28-11-2%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=-11%2F3-%282%2F3%29%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"-11%2F3-%282%2F3%29%2Ax\" we can substitute the expression \"-11%2F3-%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( " \"4%2Ax%2B-2%2Ahighlight%28%28-11%2F3-%282%2F3%29%2Ax%29%29=2\" Replace y with \"-11%2F3-%282%2F3%29%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"4%2Ax-2%2A%28-11%2F3%29-2%28-2%2F3%29x=2\" Distribute -2 to \"-11%2F3-%282%2F3%29%2Ax\"
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\n" ); document.write( " \"4%2Ax%2B22%2F3%2B%284%2F3%29%2Ax=2\" Multiply
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\n" ); document.write( " \"4%2Ax%2B22%2F3%2B%284%2F3%29%2Ax=2\" Reduce any fractions
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\n" ); document.write( " \"4%2Ax%2B%284%2F3%29%2Ax=2-22%2F3\" Subtract \"22%2F3\" from both sides
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\n" ); document.write( " \"4%2Ax%2B%284%2F3%29%2Ax=6%2F3-22%2F3\" Make 2 into a fraction with a denominator of 3
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\n" ); document.write( " \"4%2Ax%2B%284%2F3%29%2Ax=-16%2F3\" Combine the terms on the right side
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\n" ); document.write( " \"%2812%2F3%29%2Ax%2B%284%2F3%29x=-16%2F3\" Make 4 into a fraction with a denominator of 3
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\n" ); document.write( " \"%2816%2F3%29%2Ax=-16%2F3\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%283%2F16%29%2816%2F3%29%29x=%28-16%2F3%29%283%2F16%29\" Multiply both sides by \"3%2F16\". This will cancel out \"16%2F3\" and isolate x
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\n" ); document.write( " So when we multiply \"-16%2F3\" and \"3%2F16\" (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( " \"4%28-1%29-2%2Ay=2\" Plug in \"x=-1\" into the 2nd equation
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\n" ); document.write( " \"-4-2%2Ay=2\" Multiply
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\n" ); document.write( " \"-2%2Ay=2%2B4\"Add \"4\" to both sides
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\n" ); document.write( " \"-2%2Ay=6\" 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=%286%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=6%2F-2\" Multiply the terms on the right side
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\n" ); document.write( " \"y=-3\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=-3\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=-1\" and \"y=-3\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"-1\",\"-3\")
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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%2B3%2Ay=-11\"
\n" ); document.write( " \"4%2Ax-2%2Ay=2\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"2%2Ax%2B3%2Ay=-11\" (red) and \"4%2Ax-2%2Ay=2\" (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\",\"-3\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"-1\",\"-3\") into the system of equations
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\n" ); document.write( " Let \"x=-1\" and \"y=-3\". Now plug those values into the equation \"2%2Ax%2B3%2Ay=-11\"
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\n" ); document.write( " \"2%2A%28-1%29%2B3%2A%28-3%29=-11\" Plug in \"x=-1\" and \"y=-3\"
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\n" ); document.write( " \"-2-9=-11\" Multiply
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\n" ); document.write( " \"-11=-11\" Add
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\n" ); document.write( " \"-11=-11\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"-1\",\"-3\") satisfies \"2%2Ax%2B3%2Ay=-11\"
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\n" ); document.write( " Let \"x=-1\" and \"y=-3\". Now plug those values into the equation \"4%2Ax-2%2Ay=2\"
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\n" ); document.write( " \"4%2A%28-1%29-2%2A%28-3%29=2\" Plug in \"x=-1\" and \"y=-3\"
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\n" ); document.write( " \"-4%2B6=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\",\"-3\") satisfies \"4%2Ax-2%2Ay=2\"
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\n" ); document.write( " Since the solution (\"-1\",\"-3\") satisfies the system of equations
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\n" ); document.write( " \"2%2Ax%2B3%2Ay=-11\"
\n" ); document.write( " \"4%2Ax-2%2Ay=2\"
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\n" ); document.write( " this verifies our answer.
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