document.write( "Question 912766: how do you find the equation for these points {4,-8} {-3,1} \n" ); document.write( "
Algebra.Com's Answer #554029 by jim_thompson5910(35256)\"\" \"About 
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Solved by pluggable solver: Finding the Equation of a Line
First lets find the slope through the points (\"4\",\"-8\") and (\"-3\",\"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 (\"4\",\"-8\") and (\"x%5B2%5D\",\"y%5B2%5D\") is the second point (\"-3\",\"1\"))
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\n" ); document.write( " \"m=%281--8%29%2F%28-3-4%29\" Plug in \"y%5B2%5D=1\",\"y%5B1%5D=-8\",\"x%5B2%5D=-3\",\"x%5B1%5D=4\" (these are the coordinates of given points)
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\n" ); document.write( " \"m=+9%2F-7\" Subtract the terms in the numerator \"1--8\" to get \"9\". Subtract the terms in the denominator \"-3-4\" to get \"-7\"
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\n" ); document.write( " \"m=-9%2F7\" Reduce
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\n" ); document.write( " So the slope is
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\n" ); document.write( " \"m=-9%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--8=%28-9%2F7%29%28x-4%29\" Plug in \"m=-9%2F7\", \"x%5B1%5D=4\", and \"y%5B1%5D=-8\" (these values are given)
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\n" ); document.write( " \"y%2B8=%28-9%2F7%29%28x-4%29\" Rewrite \"y--8\" as \"y%2B8\"
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\n" ); document.write( " \"y%2B8=%28-9%2F7%29x%2B%28-9%2F7%29%28-4%29\" Distribute \"-9%2F7\"
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\n" ); document.write( " \"y%2B8=%28-9%2F7%29x%2B36%2F7\" Multiply \"-9%2F7\" and \"-4\" to get \"36%2F7\"
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\n" ); document.write( " \"y=%28-9%2F7%29x%2B36%2F7-8\" Subtract \"8\" from both sides to isolate y
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\n" ); document.write( " \"y=%28-9%2F7%29x-20%2F7\" Combine like terms \"36%2F7\" and \"-8\" to get \"-20%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 (\"4\",\"-8\") and (\"-3\",\"1\") is:\"y=%28-9%2F7%29x-20%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=-9%2F7\" and the y-intercept is \"b=-20%2F7\"
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\n" ); document.write( " Notice if we graph the equation \"y=%28-9%2F7%29x-20%2F7\" and plot the points (\"4\",\"-8\") and (\"-3\",\"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=%28-9%2F7%29x-20%2F7\" through the points (\"4\",\"-8\") and (\"-3\",\"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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\n" ); document.write( "\n" ); document.write( "Let me know if you need more help or if you need me to explain a step in more detail.
\n" ); document.write( "Feel free to email me at jim_thompson5910@hotmail.com
\n" ); document.write( "or you can visit my website here: http://www.freewebs.com/jimthompson5910/home.html\r
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\n" ); document.write( "\n" ); document.write( "Thanks,\r
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\n" ); document.write( "\n" ); document.write( "Jim
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