document.write( "Question 101416: find the slope intercept form of a line that passes through A(8,3) and B(-7,-5) \n" ); document.write( "
Algebra.Com's Answer #73896 by edjones(8007)\"\" \"About 
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Solved by pluggable solver: Finding the Equation of a Line
First lets find the slope through the points (\"8\",\"3\") and (\"-7\",\"-5\")
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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 (\"8\",\"3\") and (\"x%5B2%5D\",\"y%5B2%5D\") is the second point (\"-7\",\"-5\"))
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\n" ); document.write( " \"m=%28-5-3%29%2F%28-7-8%29\" Plug in \"y%5B2%5D=-5\",\"y%5B1%5D=3\",\"x%5B2%5D=-7\",\"x%5B1%5D=8\" (these are the coordinates of given points)
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\n" ); document.write( " \"m=+-8%2F-15\" Subtract the terms in the numerator \"-5-3\" to get \"-8\". Subtract the terms in the denominator \"-7-8\" to get \"-15\"
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\n" ); document.write( " \"m=8%2F15\" Reduce
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\n" ); document.write( " So the slope is
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\n" ); document.write( " \"m=8%2F15\"
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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-3=%288%2F15%29%28x-8%29\" Plug in \"m=8%2F15\", \"x%5B1%5D=8\", and \"y%5B1%5D=3\" (these values are given)
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\n" ); document.write( " \"y-3=%288%2F15%29x%2B%288%2F15%29%28-8%29\" Distribute \"8%2F15\"
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\n" ); document.write( " \"y-3=%288%2F15%29x-64%2F15\" Multiply \"8%2F15\" and \"-8\" to get \"-64%2F15\"
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\n" ); document.write( " \"y=%288%2F15%29x-64%2F15%2B3\" Add \"3\" to both sides to isolate y
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\n" ); document.write( " \"y=%288%2F15%29x-19%2F15\" Combine like terms \"-64%2F15\" and \"3\" to get \"-19%2F15\" (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 (\"8\",\"3\") and (\"-7\",\"-5\") is:\"y=%288%2F15%29x-19%2F15\"
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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=8%2F15\" and the y-intercept is \"b=-19%2F15\"
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\n" ); document.write( " Notice if we graph the equation \"y=%288%2F15%29x-19%2F15\" and plot the points (\"8\",\"3\") and (\"-7\",\"-5\"), we get this: (note: if you need help with graphing, check out this solver)
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\n" ); document.write( " Graph of \"y=%288%2F15%29x-19%2F15\" through the points (\"8\",\"3\") and (\"-7\",\"-5\")
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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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