document.write( "Question 121347: - Determine how many solutions exist
\n" ); document.write( "- Use either elimination or substitution to find the solutions (if any)
\n" ); document.write( "- Graph the two lines, labeling the x-intercepts, y-intercepts, and points of intersection \r
\n" ); document.write( "\n" ); document.write( "2x + 3y = 8 and 3x + 2y = 7
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Algebra.Com's Answer #89053 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( " \"2%2Ax%2B3%2Ay=8\"
\n" ); document.write( " \"3%2Ax%2B2%2Ay=7\"
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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=8-2%2Ax\"Subtract \"2%2Ax\" from both sides
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\n" ); document.write( " \"y=%288-2%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=8%2F3-%282%2F3%29%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"8%2F3-%282%2F3%29%2Ax\" we can substitute the expression \"8%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( " \"3%2Ax%2B2%2Ahighlight%28%288%2F3-%282%2F3%29%2Ax%29%29=7\" Replace y with \"8%2F3-%282%2F3%29%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"3%2Ax%2B2%2A%288%2F3%29%2B2%28-2%2F3%29x=7\" Distribute 2 to \"8%2F3-%282%2F3%29%2Ax\"
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\n" ); document.write( " \"3%2Ax%2B16%2F3-%284%2F3%29%2Ax=7\" Multiply
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\n" ); document.write( " \"3%2Ax%2B16%2F3-%284%2F3%29%2Ax=7\" Reduce any fractions
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\n" ); document.write( " \"3%2Ax-%284%2F3%29%2Ax=7-16%2F3\" Subtract \"16%2F3\" from both sides
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\n" ); document.write( " \"3%2Ax-%284%2F3%29%2Ax=21%2F3-16%2F3\" Make 7 into a fraction with a denominator of 3
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\n" ); document.write( " \"3%2Ax-%284%2F3%29%2Ax=5%2F3\" Combine the terms on the right side
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\n" ); document.write( " \"%289%2F3%29%2Ax-%284%2F3%29x=5%2F3\" Make 3 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=%285%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( " \"3%281%29%2B2%2Ay=7\" Plug in \"x=1\" into the 2nd equation
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\n" ); document.write( " \"3%2B2%2Ay=7\" Multiply
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\n" ); document.write( " \"2%2Ay=7-3\"Subtract \"3\" from both sides
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\n" ); document.write( " \"2%2Ay=4\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F2%29%282%29%29%2Ay=%284%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=4%2F2\" Multiply the terms on the right side
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\n" ); document.write( " \"y=2\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=2\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=1\" and \"y=2\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"1\",\"2\")
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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=8\"
\n" ); document.write( " \"3%2Ax%2B2%2Ay=7\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"2%2Ax%2B3%2Ay=8\" (red) and \"3%2Ax%2B2%2Ay=7\" (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\",\"2\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"1\",\"2\") into the system of equations
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\n" ); document.write( " Let \"x=1\" and \"y=2\". Now plug those values into the equation \"2%2Ax%2B3%2Ay=8\"
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\n" ); document.write( " \"2%2A%281%29%2B3%2A%282%29=8\" Plug in \"x=1\" and \"y=2\"
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\n" ); document.write( " \"2%2B6=8\" Multiply
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\n" ); document.write( " \"8=8\" Add
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\n" ); document.write( " \"8=8\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"1\",\"2\") satisfies \"2%2Ax%2B3%2Ay=8\"
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\n" ); document.write( " Let \"x=1\" and \"y=2\". Now plug those values into the equation \"3%2Ax%2B2%2Ay=7\"
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\n" ); document.write( " \"3%2A%281%29%2B2%2A%282%29=7\" Plug in \"x=1\" and \"y=2\"
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\n" ); document.write( " \"3%2B4=7\" Multiply
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\n" ); document.write( " \"7=7\" Add
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\n" ); document.write( " \"7=7\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"1\",\"2\") satisfies \"3%2Ax%2B2%2Ay=7\"
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\n" ); document.write( " Since the solution (\"1\",\"2\") satisfies the system of equations
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\n" ); document.write( " \"2%2Ax%2B3%2Ay=8\"
\n" ); document.write( " \"3%2Ax%2B2%2Ay=7\"
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\n" ); document.write( " this verifies our answer.
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