document.write( "Question 222456: 3x-2y=10
\n" ); document.write( "x-y=-4\r
\n" ); document.write( "\n" ); document.write( "What is the intersecting coordinates?\r
\n" ); document.write( "\n" ); document.write( "Here is what I figured:
\n" ); document.write( "3x-2y=10
\n" ); document.write( "-3x -3x
\n" ); document.write( "-2y/-2=-3x/-2 +10/-2
\n" ); document.write( "y= 3/2x-5\r
\n" ); document.write( "\n" ); document.write( "x-y=-4
\n" ); document.write( "-x -x
\n" ); document.write( "-y/y= x + 4\r
\n" ); document.write( "\n" ); document.write( "Coordinate is (2,-2)
\n" ); document.write( "My teacher marked this wrong
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Algebra.Com's Answer #166546 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=10\"
\n" ); document.write( " \"1%2Ax-1%2Ay=-4\"
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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=10-3%2Ax\"Subtract \"3%2Ax\" from both sides
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\n" ); document.write( " \"y=%2810-3%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=-5%2B%283%2F2%29%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"-5%2B%283%2F2%29%2Ax\" we can substitute the expression \"-5%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( " \"1%2Ax%2B-1%2Ahighlight%28%28-5%2B%283%2F2%29%2Ax%29%29=-4\" Replace y with \"-5%2B%283%2F2%29%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"1%2Ax-1%2A%28-5%29-1%283%2F2%29x=-4\" Distribute -1 to \"-5%2B%283%2F2%29%2Ax\"
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\n" ); document.write( " \"1%2Ax%2B5-%283%2F2%29%2Ax=-4\" Multiply
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\n" ); document.write( " \"1%2Ax%2B5-%283%2F2%29%2Ax=-4\" Reduce any fractions
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\n" ); document.write( " \"1%2Ax-%283%2F2%29%2Ax=-4-5\" Subtract \"5\" from both sides
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\n" ); document.write( " \"1%2Ax-%283%2F2%29%2Ax=-9\" Combine the terms on the right side
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\n" ); document.write( " \"%282%2F2%29%2Ax-%283%2F2%29x=-9\" Make 1 into a fraction with a denominator of 2
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\n" ); document.write( " \"%28-1%2F2%29%2Ax=-9\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%282%2F-1%29%28-1%2F2%29%29x=%28-9%2F1%29%282%2F-1%29\" Multiply both sides by \"2%2F-1\". This will cancel out \"-1%2F2\" and isolate x
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\n" ); document.write( " So when we multiply \"-9%2F1\" and \"2%2F-1\" (and simplify) we get
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\n" ); document.write( " \"x=18\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=18\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"1%2818%29-1%2Ay=-4\" Plug in \"x=18\" into the 2nd equation
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\n" ); document.write( " \"18-1%2Ay=-4\" Multiply
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\n" ); document.write( " \"-1%2Ay=-4-18\"Subtract \"18\" from both sides
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\n" ); document.write( " \"-1%2Ay=-22\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F-1%29%28-1%29%29%2Ay=%28-22%2F1%29%281%2F-1%29\" Multiply both sides by \"1%2F-1\". This will cancel out -1 on the left side.
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\n" ); document.write( " \"y=-22%2F-1\" Multiply the terms on the right side
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\n" ); document.write( " \"y=22\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=22\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=18\" and \"y=22\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"18\",\"22\")
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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=10\"
\n" ); document.write( " \"1%2Ax-1%2Ay=-4\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"3%2Ax-2%2Ay=10\" (red) and \"1%2Ax-1%2Ay=-4\" (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 (\"18\",\"22\"). This verifies our answer.
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\n" ); document.write( " -----------------------------------------------------------------------------------------------
\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"18\",\"22\") into the system of equations
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\n" ); document.write( " Let \"x=18\" and \"y=22\". Now plug those values into the equation \"3%2Ax-2%2Ay=10\"
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\n" ); document.write( " \"3%2A%2818%29-2%2A%2822%29=10\" Plug in \"x=18\" and \"y=22\"
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\n" ); document.write( " \"54-44=10\" Multiply
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\n" ); document.write( " \"10=10\" Add
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\n" ); document.write( " \"10=10\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"18\",\"22\") satisfies \"3%2Ax-2%2Ay=10\"
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\n" ); document.write( " Let \"x=18\" and \"y=22\". Now plug those values into the equation \"1%2Ax-1%2Ay=-4\"
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\n" ); document.write( " \"1%2A%2818%29-1%2A%2822%29=-4\" Plug in \"x=18\" and \"y=22\"
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\n" ); document.write( "
\n" ); document.write( " \"18-22=-4\" Multiply
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\n" ); document.write( " \"-4=-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 (\"18\",\"22\") satisfies \"1%2Ax-1%2Ay=-4\"
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\n" ); document.write( " Since the solution (\"18\",\"22\") satisfies the system of equations
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\n" ); document.write( " \"3%2Ax-2%2Ay=10\"
\n" ); document.write( " \"1%2Ax-1%2Ay=-4\"
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\n" ); document.write( " this verifies our answer.
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