document.write( "Question 106545: Find the equation of the line through the points (4,-1) and (2,-7). Write the equation in standard form with only integers.\r
\n" ); document.write( "\n" ); document.write( "Is standard form ax+by=c? If so, how do I go about puting this in standard form?
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Algebra.Com's Answer #77550 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
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Solved by pluggable solver: Finding the Equation of a Line
First lets find the slope through the points (\"4\",\"-1\") and (\"2\",\"-7\")
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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\",\"-1\") and (\"x%5B2%5D\",\"y%5B2%5D\") is the second point (\"2\",\"-7\"))
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\n" ); document.write( " \"m=%28-7--1%29%2F%282-4%29\" Plug in \"y%5B2%5D=-7\",\"y%5B1%5D=-1\",\"x%5B2%5D=2\",\"x%5B1%5D=4\" (these are the coordinates of given points)
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\n" ); document.write( " \"m=+-6%2F-2\" Subtract the terms in the numerator \"-7--1\" to get \"-6\". Subtract the terms in the denominator \"2-4\" to get \"-2\"
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\n" ); document.write( " \"m=3\" Reduce
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\n" ); document.write( " So the slope is
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\n" ); document.write( " \"m=3\"
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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--1=%283%29%28x-4%29\" Plug in \"m=3\", \"x%5B1%5D=4\", and \"y%5B1%5D=-1\" (these values are given)
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\n" ); document.write( " \"y%2B1=%283%29%28x-4%29\" Rewrite \"y--1\" as \"y%2B1\"
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\n" ); document.write( " \"y%2B1=3x%2B%283%29%28-4%29\" Distribute \"3\"
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\n" ); document.write( " \"y%2B1=3x-12\" Multiply \"3\" and \"-4\" to get \"-12%2F1\". Now reduce \"-12%2F1\" to get \"-12\"
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\n" ); document.write( " \"y=3x-12-1\" Subtract \"1\" from both sides to isolate y
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\n" ); document.write( " \"y=3x-13\" Combine like terms \"-12\" and \"-1\" to get \"-13\"
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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\",\"-1\") and (\"2\",\"-7\") is:\"y=3x-13\"
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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\" and the y-intercept is \"b=-13\"
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\n" ); document.write( " Notice if we graph the equation \"y=3x-13\" and plot the points (\"4\",\"-1\") and (\"2\",\"-7\"), we get this: (note: if you need help with graphing, check out this solver)
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\n" ); document.write( " Graph of \"y=3x-13\" through the points (\"4\",\"-1\") and (\"2\",\"-7\")
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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( "Now let's convert the equation into standard form\r
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Solved by pluggable solver: Converting Linear Equations in Standard form to Slope-Intercept Form (and vice versa)
Convert from slope-intercept form (y = mx+b) to standard form (Ax+By = C)


\"y+=+3x-13\" Start with the given equation


\"1y-3x+=+3x-13-3x\" Subtract 3x from both sides


\"-3x%2B1y+=+-13\" Simplify


\"-1%2A%28-3x%2B1y%29+=+-1%2A%28-13%29\" Multiply both sides by -1 to make the A coefficient positive (note: this step may be optional; it will depend on your teacher and/or textbook)


\"3x-1y+=+13\" Distribute and simplify


The original equation \"y+=+3x-13\" (slope-intercept form) is equivalent to \"3x-1y+=+13\" (standard form where A > 0)


The equation \"3x-1y+=+13\" is in the form \"Ax%2BBy+=+C\" where \"A+=+3\", \"B+=+-1\" and \"C+=+13\"


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