document.write( "Question 83041: 3r +5s =3
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Algebra.Com's Answer #59590 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Let r and s be x and y (they represent the same idea)\r
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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( " \"3%2Ax%2B5%2Ay=3\"
\n" ); document.write( " \"1%2Ax%2B2%2Ay=13\"
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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.
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\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 3 and 1 to some equal number, we could try to get them to the LCM.
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\n" ); document.write( " Since the LCM of 3 and 1 is 3, we need to multiply both sides of the top equation by 1 and multiply both sides of the bottom equation by -3 like this:
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\n" ); document.write( " \"1%2A%283%2Ax%2B5%2Ay%29=%283%29%2A1\" Multiply the top equation (both sides) by 1
\n" ); document.write( " \"-3%2A%281%2Ax%2B2%2Ay%29=%2813%29%2A-3\" Multiply the bottom equation (both sides) by -3
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\n" ); document.write( " So after multiplying we get this:
\n" ); document.write( " \"3%2Ax%2B5%2Ay=3\"
\n" ); document.write( " \"-3%2Ax-6%2Ay=-39\"
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\n" ); document.write( " Notice how 3 and -3 add to zero (ie \"3%2B-3=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( " \"%283%2Ax-3%2Ax%29%2B%285%2Ay-6%2Ay%29=3-39\"
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\n" ); document.write( " \"%283-3%29%2Ax%2B%285-6%29y=3-39\"
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\n" ); document.write( " \"cross%283%2B-3%29%2Ax%2B%285-6%29%2Ay=3-39\" 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( " \"-1%2Ay=-36\"
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\n" ); document.write( " \"y=-36%2F-1\" Divide both sides by \"-1\" to solve for y
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\n" ); document.write( " \"y=36\" Reduce
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\n" ); document.write( " Now plug this answer into the top equation \"3%2Ax%2B5%2Ay=3\" to solve for x
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\n" ); document.write( " \"3%2Ax%2B5%2836%29=3\" Plug in \"y=36\"
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\n" ); document.write( " \"3%2Ax%2B180=3\" Multiply
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\n" ); document.write( " \"3%2Ax=3-180\" Subtract \"180\" from both sides
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\n" ); document.write( " \"3%2Ax=-177\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F3%29%283%29%29%2Ax=%28-177%29%281%2F3%29\" Multiply both sides by \"1%2F3\". This will cancel out \"3\" on the left side.
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\n" ); document.write( " \"x=-59\" 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=-59\", \"y=36\"
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\n" ); document.write( " which also looks like
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\n" ); document.write( " (\"-59\", \"36\")
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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( " \"3%2Ax%2B5%2Ay=3\"
\n" ); document.write( " \"1%2Ax%2B2%2Ay=13\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"3%2Ax%2B5%2Ay=3\" (red) \"1%2Ax%2B2%2Ay=13\" (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( " and we can see that the two equations intersect at (\"-59\",\"36\"). This verifies our answer.

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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( " \"3%2Ax%2B5%2Ay=3\"
\n" ); document.write( " \"1%2Ax%2B2%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=3-3%2Ax\"Subtract \"3%2Ax\" from both sides
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\n" ); document.write( " \"y=%283-3%2Ax%29%2F5\" 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=3%2F5-%283%2F5%29%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"3%2F5-%283%2F5%29%2Ax\" we can substitute the expression \"3%2F5-%283%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( " \"1%2Ax%2B2%2Ahighlight%28%283%2F5-%283%2F5%29%2Ax%29%29=13\" Replace y with \"3%2F5-%283%2F5%29%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"1%2Ax%2B2%2A%283%2F5%29%2B2%28-3%2F5%29x=13\" Distribute 2 to \"3%2F5-%283%2F5%29%2Ax\"
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\n" ); document.write( " \"1%2Ax%2B6%2F5-%286%2F5%29%2Ax=13\" Multiply
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\n" ); document.write( " \"1%2Ax%2B6%2F5-%286%2F5%29%2Ax=13\" Reduce any fractions
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\n" ); document.write( " \"1%2Ax-%286%2F5%29%2Ax=13-6%2F5\" Subtract \"6%2F5\" from both sides
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\n" ); document.write( " \"1%2Ax-%286%2F5%29%2Ax=65%2F5-6%2F5\" Make 13 into a fraction with a denominator of 5
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\n" ); document.write( " \"1%2Ax-%286%2F5%29%2Ax=59%2F5\" Combine the terms on the right side
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\n" ); document.write( " \"%285%2F5%29%2Ax-%286%2F5%29x=59%2F5\" Make 1 into a fraction with a denominator of 5
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\n" ); document.write( " \"%28-1%2F5%29%2Ax=59%2F5\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%285%2F-1%29%28-1%2F5%29%29x=%2859%2F5%29%285%2F-1%29\" Multiply both sides by \"5%2F-1\". This will cancel out \"-1%2F5\" and isolate x
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\n" ); document.write( " So when we multiply \"59%2F5\" and \"5%2F-1\" (and simplify) we get
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\n" ); document.write( " \"x=-59\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=-59\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"1%28-59%29%2B2%2Ay=13\" Plug in \"x=-59\" into the 2nd equation
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\n" ); document.write( " \"-59%2B2%2Ay=13\" Multiply
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\n" ); document.write( " \"2%2Ay=13%2B59\"Add \"59\" to both sides
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\n" ); document.write( " \"2%2Ay=72\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F2%29%282%29%29%2Ay=%2872%2F1%29%281%2F2%29\" Multiply both sides by \"1%2F2\". This will cancel out 2 on the left side.
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\n" ); document.write( " \"y=72%2F2\" Multiply the terms on the right side
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\n" ); document.write( " \"y=36\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=36\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=-59\" and \"y=36\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"-59\",\"36\")
\n" ); document.write( "
\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( " \"3%2Ax%2B5%2Ay=3\"
\n" ); document.write( " \"1%2Ax%2B2%2Ay=13\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"3%2Ax%2B5%2Ay=3\" (red) and \"1%2Ax%2B2%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 (\"-59\",\"36\"). This verifies our answer.
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\n" ); document.write( " Plug in (\"-59\",\"36\") into the system of equations
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\n" ); document.write( " Let \"x=-59\" and \"y=36\". Now plug those values into the equation \"3%2Ax%2B5%2Ay=3\"
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\n" ); document.write( " \"3%2A%28-59%29%2B5%2A%2836%29=3\" Plug in \"x=-59\" and \"y=36\"
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\n" ); document.write( " \"-177%2B180=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 (\"-59\",\"36\") satisfies \"3%2Ax%2B5%2Ay=3\"
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\n" ); document.write( " Let \"x=-59\" and \"y=36\". Now plug those values into the equation \"1%2Ax%2B2%2Ay=13\"
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\n" ); document.write( " \"1%2A%28-59%29%2B2%2A%2836%29=13\" Plug in \"x=-59\" and \"y=36\"
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\n" ); document.write( "
\n" ); document.write( " \"-59%2B72=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( "
\n" ); document.write( " So the solution (\"-59\",\"36\") satisfies \"1%2Ax%2B2%2Ay=13\"
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\n" ); document.write( " Since the solution (\"-59\",\"36\") satisfies the system of equations
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\n" ); document.write( " \"3%2Ax%2B5%2Ay=3\"
\n" ); document.write( " \"1%2Ax%2B2%2Ay=13\"
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\n" ); document.write( " this verifies our answer.
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