document.write( "Question 100461: write an equation for the line containing each pair of points\r
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Algebra.Com's Answer #73134 by edjones(8007)\"\" \"About 
You can put this solution on YOUR website!
(-2,-4) (5,-1)
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Solved by pluggable solver: Finding the Equation of a Line
First lets find the slope through the points (\"-2\",\"-4\") and (\"5\",\"-1\")
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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 (\"-2\",\"-4\") and (\"x%5B2%5D\",\"y%5B2%5D\") is the second point (\"5\",\"-1\"))
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\n" ); document.write( " \"m=%28-1--4%29%2F%285--2%29\" Plug in \"y%5B2%5D=-1\",\"y%5B1%5D=-4\",\"x%5B2%5D=5\",\"x%5B1%5D=-2\" (these are the coordinates of given points)
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\n" ); document.write( " \"m=+3%2F7\" Subtract the terms in the numerator \"-1--4\" to get \"3\". Subtract the terms in the denominator \"5--2\" to get \"7\"
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\n" ); document.write( " So the slope is
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\n" ); document.write( " \"m=3%2F7\"
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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--4=%283%2F7%29%28x--2%29\" Plug in \"m=3%2F7\", \"x%5B1%5D=-2\", and \"y%5B1%5D=-4\" (these values are given)
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\n" ); document.write( " \"y%2B4=%283%2F7%29%28x--2%29\" Rewrite \"y--4\" as \"y%2B4\"
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\n" ); document.write( " \"y%2B4=%283%2F7%29%28x%2B2%29\" Rewrite \"x--2\" as \"x%2B2\"
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\n" ); document.write( " \"y%2B4=%283%2F7%29x%2B%283%2F7%29%282%29\" Distribute \"3%2F7\"
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\n" ); document.write( " \"y%2B4=%283%2F7%29x%2B6%2F7\" Multiply \"3%2F7\" and \"2\" to get \"6%2F7\"
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\n" ); document.write( " \"y=%283%2F7%29x%2B6%2F7-4\" Subtract \"4\" from both sides to isolate y
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\n" ); document.write( " \"y=%283%2F7%29x-22%2F7\" Combine like terms \"6%2F7\" and \"-4\" to get \"-22%2F7\" (note: if you need help with combining fractions, check out this solver)
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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 (\"-2\",\"-4\") and (\"5\",\"-1\") is:\"y=%283%2F7%29x-22%2F7\"
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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=3%2F7\" and the y-intercept is \"b=-22%2F7\"
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\n" ); document.write( " Notice if we graph the equation \"y=%283%2F7%29x-22%2F7\" and plot the points (\"-2\",\"-4\") and (\"5\",\"-1\"), we get this: (note: if you need help with graphing, check out this solver)
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\n" ); document.write( " Graph of \"y=%283%2F7%29x-22%2F7\" through the points (\"-2\",\"-4\") and (\"5\",\"-1\")
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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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