document.write( "Question 1187947: -4,7 and 2,-1 \n" ); document.write( "
Algebra.Com's Answer #818965 by MathLover1(20850)\"\" \"About 
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\n" ); document.write( "assuming that\r
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Solved by pluggable solver: Finding the Equation of a Line
First lets find the slope through the points (\"-4\",\"7\") and (\"2\",\"-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\",\"7\") and (\"x%5B2%5D\",\"y%5B2%5D\") is the second point (\"2\",\"-1\"))
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\n" ); document.write( " \"m=%28-1-7%29%2F%282--4%29\" Plug in \"y%5B2%5D=-1\",\"y%5B1%5D=7\",\"x%5B2%5D=2\",\"x%5B1%5D=-4\" (these are the coordinates of given points)
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\n" ); document.write( " \"m=+-8%2F6\" Subtract the terms in the numerator \"-1-7\" to get \"-8\". Subtract the terms in the denominator \"2--4\" to get \"6\"
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\n" ); document.write( " \"m=-4%2F3\" Reduce
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\n" ); document.write( " So the slope is
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\n" ); document.write( " \"m=-4%2F3\"
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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-7=%28-4%2F3%29%28x--4%29\" Plug in \"m=-4%2F3\", \"x%5B1%5D=-4\", and \"y%5B1%5D=7\" (these values are given)
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\n" ); document.write( " \"y-7=%28-4%2F3%29%28x%2B4%29\" Rewrite \"x--4\" as \"x%2B4\"
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\n" ); document.write( " \"y-7=%28-4%2F3%29x%2B%28-4%2F3%29%284%29\" Distribute \"-4%2F3\"
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\n" ); document.write( " \"y-7=%28-4%2F3%29x-16%2F3\" Multiply \"-4%2F3\" and \"4\" to get \"-16%2F3\"
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\n" ); document.write( " \"y=%28-4%2F3%29x-16%2F3%2B7\" Add \"7\" to both sides to isolate y
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\n" ); document.write( " \"y=%28-4%2F3%29x%2B5%2F3\" Combine like terms \"-16%2F3\" and \"7\" to get \"5%2F3\" (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\",\"7\") and (\"2\",\"-1\") is:\"y=%28-4%2F3%29x%2B5%2F3\"
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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=-4%2F3\" and the y-intercept is \"b=5%2F3\"
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\n" ); document.write( " Notice if we graph the equation \"y=%28-4%2F3%29x%2B5%2F3\" and plot the points (\"-4\",\"7\") and (\"2\",\"-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=%28-4%2F3%29x%2B5%2F3\" through the points (\"-4\",\"7\") and (\"2\",\"-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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