document.write( "Question 120266: solve one using addition and one using substitution.
\n" ); document.write( "State which method your are using for which system\r
\n" ); document.write( "\n" ); document.write( "a. 4x-3y=10 and y -20=-6x
\n" ); document.write( "b. y= 3x + 6 and =6x + 2y = 12\r
\n" ); document.write( "\n" ); document.write( "Thanks
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Algebra.Com's Answer #88142 by MathLover1(20855)\"\" \"About 
You can put this solution on YOUR website!
\r
\n" ); document.write( "\n" ); document.write( "a. \r
\n" ); document.write( "\n" ); document.write( "\"4x-3y=10\" ….this is written in the standard form \r
\n" ); document.write( "\n" ); document.write( "\"y+-20=-6x\"….write this one in the standard form too\r
\n" ); document.write( "\n" ); document.write( "\"6x+%2B+y+=20\"….\r
\n" ); document.write( "\n" ); document.write( "Here is solution (using addition):\r
\n" ); document.write( "\n" ); document.write( "\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
Solved by pluggable solver: Solving a System of Linear Equations by Elimination/Addition

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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-3%2Ay=10\"
\n" ); document.write( " \"6%2Ax%2B1%2Ay=20\"
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\n" ); document.write( " In order to solve for one variable, we must eliminate the other variable. So if we wanted to solve for y, we would have to eliminate x (or vice versa).
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\n" ); document.write( " So lets eliminate x. In order to do that, we need to have both x coefficients that are equal but have opposite signs (for instance 2 and -2 are equal but have opposite signs). This way they will add to zero.
\n" ); document.write( "
\n" ); document.write( " So to make the x coefficients equal but opposite, we need to multiply both x coefficients by some number to get them to an equal number. So if we wanted to get 4 and 6 to some equal number, we could try to get them to the LCM.
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\n" ); document.write( " Since the LCM of 4 and 6 is 12, we need to multiply both sides of the top equation by 3 and multiply both sides of the bottom equation by -2 like this:
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\n" ); document.write( " \"3%2A%284%2Ax-3%2Ay%29=%2810%29%2A3\" Multiply the top equation (both sides) by 3
\n" ); document.write( " \"-2%2A%286%2Ax%2B1%2Ay%29=%2820%29%2A-2\" Multiply the bottom equation (both sides) by -2
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\n" ); document.write( "
\n" ); document.write( " So after multiplying we get this:
\n" ); document.write( " \"12%2Ax-9%2Ay=30\"
\n" ); document.write( " \"-12%2Ax-2%2Ay=-40\"
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\n" ); document.write( " Notice how 12 and -12 add to zero (ie \"12%2B-12=0\")
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\n" ); document.write( " Now add the equations together. In order to add 2 equations, group like terms and combine them
\n" ); document.write( " \"%2812%2Ax-12%2Ax%29-9%2Ay-2%2Ay%29=30-40\"
\n" ); document.write( "
\n" ); document.write( " \"%2812-12%29%2Ax-9-2%29y=30-40\"
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\n" ); document.write( " \"cross%2812%2B-12%29%2Ax%2B%28-9-2%29%2Ay=30-40\" Notice the x coefficients add to zero and cancel out. This means we've eliminated x altogether.
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\n" ); document.write( " So after adding and canceling out the x terms we're left with:
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\n" ); document.write( " \"-11%2Ay=-10\"
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\n" ); document.write( " \"y=-10%2F-11\" Divide both sides by \"-11\" to solve for y
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\n" ); document.write( " \"y=10%2F11\" Reduce
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\n" ); document.write( " Now plug this answer into the top equation \"4%2Ax-3%2Ay=10\" to solve for x
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\n" ); document.write( " \"4%2Ax-3%2810%2F11%29=10\" Plug in \"y=10%2F11\"
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\n" ); document.write( "
\n" ); document.write( " \"4%2Ax-30%2F11=10\" Multiply
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\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"4%2Ax-30%2F11=10\" Reduce
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\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"4%2Ax=10%2B30%2F11\" Subtract \"-30%2F11\" from both sides
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\n" ); document.write( " \"4%2Ax=110%2F11%2B30%2F11\" Make 10 into a fraction with a denominator of 11
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\n" ); document.write( " \"4%2Ax=140%2F11\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F4%29%284%29%29%2Ax=%28140%2F11%29%281%2F4%29\" Multiply both sides by \"1%2F4\". This will cancel out \"4\" on the left side.
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\n" ); document.write( " \"x=35%2F11\" Multiply the terms on the right side
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\n" ); document.write( " So our answer is
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\n" ); document.write( " \"x=35%2F11\", \"y=10%2F11\"
\n" ); document.write( "
\n" ); document.write( " which also looks like
\n" ); document.write( "
\n" ); document.write( " (\"35%2F11\", \"10%2F11\")
\n" ); document.write( "
\n" ); document.write( " Notice if we graph the equations (if you need help with graphing, check out this solver)
\n" ); document.write( "
\n" ); document.write( " \"4%2Ax-3%2Ay=10\"
\n" ); document.write( " \"6%2Ax%2B1%2Ay=20\"
\n" ); document.write( "
\n" ); document.write( " we get
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\n" ); document.write( "
\n" ); document.write( " graph of \"4%2Ax-3%2Ay=10\" (red) \"6%2Ax%2B1%2Ay=20\" (green) (hint: you may have to solve for y to graph these) and the intersection of the lines (blue circle).
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\n" ); document.write( "
\n" ); document.write( " and we can see that the two equations intersect at (\"35%2F11\",\"10%2F11\"). This verifies our answer.

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\n" ); document.write( "\n" ); document.write( "b. \r
\n" ); document.write( "\n" ); document.write( "\"+y=+3x+%2B+6+\"…. write this one in the standard form\r
\n" ); document.write( "\n" ); document.write( "\"-3x+%2B+y=+6+\"….\r
\n" ); document.write( "\n" ); document.write( "\"+6x+%2B+2y+=+12\"…. this is the standard form\r
\n" ); document.write( "\n" ); document.write( "Here is solution (using substitution):\r
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\n" ); document.write( "\n" ); document.write( "\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
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
\n" ); document.write( "
\n" ); document.write( " \"-3%2Ax%2B1%2Ay=6\"
\n" ); document.write( " \"6%2Ax%2B2%2Ay=12\"
\n" ); document.write( "
\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=6%2B3%2Ax\"Add \"3%2Ax\" to both sides
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\n" ); document.write( " \"y=%286%2B3%2Ax%29\" Divide both sides by 1.
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\n" ); document.write( "
\n" ); document.write( " Which breaks down and reduces to
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\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"y=6%2B3%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"6%2B3%2Ax\" we can substitute the expression \"6%2B3%2Ax\" into y of the 2nd equation. This will eliminate y so we can solve for x.
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\n" ); document.write( "
\n" ); document.write( " \"6%2Ax%2B2%2Ahighlight%28%286%2B3%2Ax%29%29=12\" Replace y with \"6%2B3%2Ax\". Since this eliminates y, we can now solve for x.
\n" ); document.write( "
\n" ); document.write( " \"6%2Ax%2B2%2A%286%29%2B2%283%29x=12\" Distribute 2 to \"6%2B3%2Ax\"
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\n" ); document.write( " \"6%2Ax%2B12%2B6%2Ax=12\" Multiply
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\n" ); document.write( "
\n" ); document.write( " \"6%2Ax%2B12%2B6%2Ax=12\" Reduce any fractions
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\n" ); document.write( " \"6%2Ax%2B6%2Ax=12-12\" Subtract \"12\" from both sides
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\n" ); document.write( " \"6%2Ax%2B6%2Ax=0\" Combine the terms on the right side
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\n" ); document.write( " \"12%2Ax=0\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F12%29%2812%2F1%29%29x=%280%2F1%29%281%2F12%29\" Multiply both sides by \"1%2F12\". This will cancel out \"12%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"0%2F1\" and \"1%2F12\" (and simplify) we get
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\n" ); document.write( " \"x=0\" <---------------------------------One answer
\n" ); document.write( "
\n" ); document.write( " Now that we know that \"x=0\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"6%280%29%2B2%2Ay=12\" Plug in \"x=0\" into the 2nd equation
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\n" ); document.write( " \"0%2B2%2Ay=12\" Multiply
\n" ); document.write( "
\n" ); document.write( " \"2%2Ay=12%2B0\"Add \"0\" to both sides
\n" ); document.write( "
\n" ); document.write( " \"2%2Ay=12\" Combine the terms on the right side
\n" ); document.write( "
\n" ); document.write( " \"cross%28%281%2F2%29%282%29%29%2Ay=%2812%2F1%29%281%2F2%29\" Multiply both sides by \"1%2F2\". This will cancel out 2 on the left side.
\n" ); document.write( "
\n" ); document.write( " \"y=12%2F2\" Multiply the terms on the right side
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"y=6\" Reduce
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So this is the other answer
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\n" ); document.write( "
\n" ); document.write( " \"y=6\"<---------------------------------Other answer
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\n" ); document.write( "
\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=0\" and \"y=6\"
\n" ); document.write( "
\n" ); document.write( " which can also look like
\n" ); document.write( "
\n" ); document.write( " (\"0\",\"6\")
\n" ); document.write( "
\n" ); document.write( " Notice if we graph the equations (if you need help with graphing, check out this solver)
\n" ); document.write( "
\n" ); document.write( " \"-3%2Ax%2B1%2Ay=6\"
\n" ); document.write( " \"6%2Ax%2B2%2Ay=12\"
\n" ); document.write( "
\n" ); document.write( " we get
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " graph of \"-3%2Ax%2B1%2Ay=6\" (red) and \"6%2Ax%2B2%2Ay=12\" (green) (hint: you may have to solve for y to graph these) intersecting at the blue circle.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " and we can see that the two equations intersect at (\"0\",\"6\"). This verifies our answer.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " -----------------------------------------------------------------------------------------------
\n" ); document.write( " Check:
\n" ); document.write( "
\n" ); document.write( " Plug in (\"0\",\"6\") into the system of equations
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\n" ); document.write( "
\n" ); document.write( " Let \"x=0\" and \"y=6\". Now plug those values into the equation \"-3%2Ax%2B1%2Ay=6\"
\n" ); document.write( "
\n" ); document.write( " \"-3%2A%280%29%2B1%2A%286%29=6\" Plug in \"x=0\" and \"y=6\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"0%2B6=6\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"6=6\" Add
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"6=6\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( "
\n" ); document.write( " So the solution (\"0\",\"6\") satisfies \"-3%2Ax%2B1%2Ay=6\"
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\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Let \"x=0\" and \"y=6\". Now plug those values into the equation \"6%2Ax%2B2%2Ay=12\"
\n" ); document.write( "
\n" ); document.write( " \"6%2A%280%29%2B2%2A%286%29=12\" Plug in \"x=0\" and \"y=6\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"0%2B12=12\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"12=12\" Add
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"12=12\" Reduce. Since this equation is true the solution works.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the solution (\"0\",\"6\") satisfies \"6%2Ax%2B2%2Ay=12\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Since the solution (\"0\",\"6\") satisfies the system of equations
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-3%2Ax%2B1%2Ay=6\"
\n" ); document.write( " \"6%2Ax%2B2%2Ay=12\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " this verifies our answer.
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