document.write( "Question 107643This question is from textbook
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\n" ); document.write( "5x+4y=8
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Algebra.Com's Answer #78403 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( " \"3%2Ax-2%2Ay=7\"
\n" ); document.write( " \"5%2Ax%2B4%2Ay=8\"
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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( " \"-2%2Ay=7-3%2Ax\"Subtract \"3%2Ax\" from both sides
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\n" ); document.write( " \"y=%287-3%2Ax%29%2F-2\" Divide both sides by -2.
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\n" ); document.write( " Which breaks down and reduces to
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\n" ); document.write( " \"y=-7%2F2%2B%283%2F2%29%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"-7%2F2%2B%283%2F2%29%2Ax\" we can substitute the expression \"-7%2F2%2B%283%2F2%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%2B4%2Ahighlight%28%28-7%2F2%2B%283%2F2%29%2Ax%29%29=8\" Replace y with \"-7%2F2%2B%283%2F2%29%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"5%2Ax%2B4%2A%28-7%2F2%29%2B4%283%2F2%29x=8\" Distribute 4 to \"-7%2F2%2B%283%2F2%29%2Ax\"
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\n" ); document.write( " \"5%2Ax-28%2F2%2B%2812%2F2%29%2Ax=8\" Multiply
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\n" ); document.write( " \"5%2Ax-14%2B6%2Ax=8\" Reduce any fractions
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\n" ); document.write( " \"5%2Ax%2B6%2Ax=8%2B14\"Add \"14\" to both sides
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\n" ); document.write( " \"5%2Ax%2B6%2Ax=22\" Combine the terms on the right side
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\n" ); document.write( " \"11%2Ax=22\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F11%29%2811%2F1%29%29x=%2822%2F1%29%281%2F11%29\" Multiply both sides by \"1%2F11\". This will cancel out \"11%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"22%2F1\" and \"1%2F11\" (and simplify) we get
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\n" ); document.write( " \"x=2\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=2\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"5%282%29%2B4%2Ay=8\" Plug in \"x=2\" into the 2nd equation
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\n" ); document.write( " \"10%2B4%2Ay=8\" Multiply
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\n" ); document.write( " \"4%2Ay=8-10\"Subtract \"10\" from both sides
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\n" ); document.write( " \"4%2Ay=-2\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F4%29%284%29%29%2Ay=%28-2%2F1%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( " \"y=-2%2F4\" Multiply the terms on the right side
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\n" ); document.write( " \"y=-1%2F2\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=-1%2F2\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=2\" and \"y=-1%2F2\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"2\",\"-1%2F2\")
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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-2%2Ay=7\"
\n" ); document.write( " \"5%2Ax%2B4%2Ay=8\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"3%2Ax-2%2Ay=7\" (red) and \"5%2Ax%2B4%2Ay=8\" (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 (\"2\",\"-1%2F2\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"2\",\"-1%2F2\") into the system of equations
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\n" ); document.write( " Let \"x=2\" and \"y=-1%2F2\". Now plug those values into the equation \"3%2Ax-2%2Ay=7\"
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\n" ); document.write( " \"3%2A%282%29-2%2A%28-1%2F2%29=7\" Plug in \"x=2\" and \"y=-1%2F2\"
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\n" ); document.write( " \"6%2B2%2F2=7\" Multiply
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\n" ); document.write( " \"14%2F2=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 (\"2\",\"-1%2F2\") satisfies \"3%2Ax-2%2Ay=7\"
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\n" ); document.write( " Let \"x=2\" and \"y=-1%2F2\". Now plug those values into the equation \"5%2Ax%2B4%2Ay=8\"
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\n" ); document.write( " \"5%2A%282%29%2B4%2A%28-1%2F2%29=8\" Plug in \"x=2\" and \"y=-1%2F2\"
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\n" ); document.write( " \"10-4%2F2=8\" Multiply
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\n" ); document.write( " \"16%2F2=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 (\"2\",\"-1%2F2\") satisfies \"5%2Ax%2B4%2Ay=8\"
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\n" ); document.write( " Since the solution (\"2\",\"-1%2F2\") satisfies the system of equations
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\n" ); document.write( " \"3%2Ax-2%2Ay=7\"
\n" ); document.write( " \"5%2Ax%2B4%2Ay=8\"
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\n" ); document.write( " this verifies our answer.
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