document.write( "Question 83597: 1. Write the equation of the line through (1,2) and (-3,6) in the y=mx+b format. \r
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\n" ); document.write( " x + y - z = 0
\n" ); document.write( " 2x - y + z = 6
\n" ); document.write( " -x + y + z = 8
\n" ); document.write( "Show your answers as (x,y,z)
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Algebra.Com's Answer #60107 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
1.
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Solved by pluggable solver: Finding the Equation of a Line
First lets find the slope through the points (\"1\",\"2\") and (\"-3\",\"6\")
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\n" ); document.write( " \"m=%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29\" Start with the slope formula (note: (\"x%5B1%5D\",\"y%5B1%5D\") is the first point (\"1\",\"2\") and (\"x%5B2%5D\",\"y%5B2%5D\") is the second point (\"-3\",\"6\"))
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\n" ); document.write( " \"m=%286-2%29%2F%28-3-1%29\" Plug in \"y%5B2%5D=6\",\"y%5B1%5D=2\",\"x%5B2%5D=-3\",\"x%5B1%5D=1\" (these are the coordinates of given points)
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\n" ); document.write( " \"m=+4%2F-4\" Subtract the terms in the numerator \"6-2\" to get \"4\". Subtract the terms in the denominator \"-3-1\" to get \"-4\"
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\n" ); document.write( " \"m=-1\" Reduce
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\n" ); document.write( " So the slope is
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\n" ); document.write( " \"m=-1\"
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\n" ); document.write( "Now let's use the point-slope formula to find the equation of the line:
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\n" ); document.write( " ------Point-Slope Formula------
\n" ); document.write( " \"y-y%5B1%5D=m%28x-x%5B1%5D%29\" where \"m\" is the slope, and (\"x%5B1%5D\",\"y%5B1%5D\") is one of the given points
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\n" ); document.write( " So lets use the Point-Slope Formula to find the equation of the line
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\n" ); document.write( " \"y-2=%28-1%29%28x-1%29\" Plug in \"m=-1\", \"x%5B1%5D=1\", and \"y%5B1%5D=2\" (these values are given)
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\n" ); document.write( " \"y-2=-x%2B%28-1%29%28-1%29\" Distribute \"-1\"
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\n" ); document.write( " \"y-2=-x%2B1\" Multiply \"-1\" and \"-1\" to get \"1%2F1\". Now reduce \"1%2F1\" to get \"1\"
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\n" ); document.write( " \"y=-x%2B1%2B2\" Add \"2\" to both sides to isolate y
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\n" ); document.write( " \"y=-x%2B3\" Combine like terms \"1\" and \"2\" to get \"3\"
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\n" ); document.write( " Answer:
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\n" ); document.write( " So the equation of the line which goes through the points (\"1\",\"2\") and (\"-3\",\"6\") is:\"y=-x%2B3\"
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\n" ); document.write( " The equation is now in \"y=mx%2Bb\" form (which is slope-intercept form) where the slope is \"m=-1\" and the y-intercept is \"b=3\"
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\n" ); document.write( " Notice if we graph the equation \"y=-x%2B3\" and plot the points (\"1\",\"2\") and (\"-3\",\"6\"), we get this: (note: if you need help with graphing, check out this solver)
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\n" ); document.write( " Graph of \"y=-x%2B3\" through the points (\"1\",\"2\") and (\"-3\",\"6\")
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\n" ); document.write( " Notice how the two points lie on the line. This graphically verifies our answer.
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\n" ); document.write( "\n" ); document.write( "2.\r
\n" ); document.write( "\n" ); document.write( "Start with the given system and label the equations\r
\n" ); document.write( "\n" ); document.write( "\"x+%2B+y+-+z+=+0\" Equation 1
\n" ); document.write( "\"2x+-+y+%2B+z+=+6\" Equation 2
\n" ); document.write( "\"-x+%2B+y+%2B+z+=+8\" Equation 3
\n" ); document.write( "\"3x=6\" Add equations 1 and 2
\n" ); document.write( "\"x=2\" Divide both sides by 3\r
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\n" ); document.write( "\n" ); document.write( "Now lets use this info to find another variable\r
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\n" ); document.write( "\n" ); document.write( "\"2%2A2-y%2Bz=6\" Plug in x=2 into equation 2 to get Equation 4
\n" ); document.write( "\"4-y%2Bz=6\" Multiply
\n" ); document.write( "\"-2%2By%2Bz=8\" Plug in x=2 into equation 3 to get Equation 5
\n" ); document.write( "\"-%28-2%2By%2Bz%29=-8\" Multiply equation 3 by -1\r
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\n" ); document.write( "\n" ); document.write( "So now we have the equations\r
\n" ); document.write( "\n" ); document.write( "\"4-y%2Bz=6\" Equation 4
\n" ); document.write( "\"2-y-z=-8\" Equation 5
\n" ); document.write( "\"6-2y=-2\" Add equations 4 and 5
\n" ); document.write( "\"-2y=-8\" Subtract 6 from both sides
\n" ); document.write( "\"y=4\" Divide both sides by -2\r
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\n" ); document.write( "\n" ); document.write( "Now lets use this to find z\r
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\n" ); document.write( "\n" ); document.write( "\"2%2B4-z=0\" Plug in x=2 and y=4 into Equation 1 (at this point any equation will do)
\n" ); document.write( "\"6-z=0\" Add
\n" ); document.write( "\"-z=-6\" Subtract
\n" ); document.write( "\"z=6\" Divide\r
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\n" ); document.write( "\n" ); document.write( "So our solution is \r
\n" ); document.write( "\n" ); document.write( "(2,4,6)
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