document.write( "Question 701810: Solve each system by substitution
\n" ); document.write( "4y-2x=-2 and x+3y=4
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Algebra.Com's Answer #432604 by mouk(232)\"\" \"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( " \"1%2Ax%2B3%2Ay=4\"
\n" ); document.write( " \"-2%2Ax%2B4%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=4-1%2Ax\"Subtract \"1%2Ax\" from both sides
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\n" ); document.write( " \"y=%284-1%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=4%2F3-%281%2F3%29%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"4%2F3-%281%2F3%29%2Ax\" we can substitute the expression \"4%2F3-%281%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( " \"-2%2Ax%2B4%2Ahighlight%28%284%2F3-%281%2F3%29%2Ax%29%29=-2\" Replace y with \"4%2F3-%281%2F3%29%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"-2%2Ax%2B4%2A%284%2F3%29%2B4%28-1%2F3%29x=-2\" Distribute 4 to \"4%2F3-%281%2F3%29%2Ax\"
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\n" ); document.write( " \"-2%2Ax%2B16%2F3-%284%2F3%29%2Ax=-2\" Multiply
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\n" ); document.write( " \"-2%2Ax%2B16%2F3-%284%2F3%29%2Ax=-2\" Reduce any fractions
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\n" ); document.write( " \"-2%2Ax-%284%2F3%29%2Ax=-2-16%2F3\" Subtract \"16%2F3\" from both sides
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\n" ); document.write( " \"-2%2Ax-%284%2F3%29%2Ax=-6%2F3-16%2F3\" Make -2 into a fraction with a denominator of 3
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\n" ); document.write( " \"-2%2Ax-%284%2F3%29%2Ax=-22%2F3\" Combine the terms on the right side
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\n" ); document.write( " \"%28-6%2F3%29%2Ax-%284%2F3%29x=-22%2F3\" Make -2 into a fraction with a denominator of 3
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\n" ); document.write( " \"%28-10%2F3%29%2Ax=-22%2F3\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%283%2F-10%29%28-10%2F3%29%29x=%28-22%2F3%29%283%2F-10%29\" Multiply both sides by \"3%2F-10\". This will cancel out \"-10%2F3\" and isolate x
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\n" ); document.write( " So when we multiply \"-22%2F3\" and \"3%2F-10\" (and simplify) we get
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\n" ); document.write( " \"x=11%2F5\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=11%2F5\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"-2%2811%2F5%29%2B4%2Ay=-2\" Plug in \"x=11%2F5\" into the 2nd equation
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\n" ); document.write( " \"-22%2F5%2B4%2Ay=-2\" Multiply
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\n" ); document.write( " \"4%2Ay=-2%2B22%2F5\"Add \"22%2F5\" to both sides
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\n" ); document.write( " \"4%2Ay=-10%2F5%2B22%2F5\" Make -2 into a fraction with a denominator of 5
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\n" ); document.write( " \"4%2Ay=12%2F5\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F4%29%284%29%29%2Ay=%2812%2F5%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=12%2F20\" Multiply the terms on the right side
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\n" ); document.write( " \"y=3%2F5\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=3%2F5\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=11%2F5\" and \"y=3%2F5\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"11%2F5\",\"3%2F5\")
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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( " \"1%2Ax%2B3%2Ay=4\"
\n" ); document.write( " \"-2%2Ax%2B4%2Ay=-2\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"1%2Ax%2B3%2Ay=4\" (red) and \"-2%2Ax%2B4%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 (\"11%2F5\",\"3%2F5\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"11%2F5\",\"3%2F5\") into the system of equations
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\n" ); document.write( " Let \"x=11%2F5\" and \"y=3%2F5\". Now plug those values into the equation \"1%2Ax%2B3%2Ay=4\"
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\n" ); document.write( " \"1%2A%2811%2F5%29%2B3%2A%283%2F5%29=4\" Plug in \"x=11%2F5\" and \"y=3%2F5\"
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\n" ); document.write( " \"11%2F5%2B9%2F5=4\" Multiply
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\n" ); document.write( " \"20%2F5=4\" Add
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\n" ); document.write( " \"4=4\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"11%2F5\",\"3%2F5\") satisfies \"1%2Ax%2B3%2Ay=4\"
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\n" ); document.write( " Let \"x=11%2F5\" and \"y=3%2F5\". Now plug those values into the equation \"-2%2Ax%2B4%2Ay=-2\"
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\n" ); document.write( " \"-2%2A%2811%2F5%29%2B4%2A%283%2F5%29=-2\" Plug in \"x=11%2F5\" and \"y=3%2F5\"
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\n" ); document.write( " \"-22%2F5%2B12%2F5=-2\" Multiply
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\n" ); document.write( " \"-10%2F5=-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 (\"11%2F5\",\"3%2F5\") satisfies \"-2%2Ax%2B4%2Ay=-2\"
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\n" ); document.write( " Since the solution (\"11%2F5\",\"3%2F5\") satisfies the system of equations
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\n" ); document.write( " \"1%2Ax%2B3%2Ay=4\"
\n" ); document.write( " \"-2%2Ax%2B4%2Ay=-2\"
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\n" ); document.write( " this verifies our answer.
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