document.write( "Question 84243: a. Find the equation of the straight line joinging the points (1,2) and (-3,5).
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\n" ); document.write( "d. Algebraically verify your answer to above part of the problem.
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Algebra.Com's Answer #60669 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
a.
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Solved by pluggable solver: Finding the Equation of a Line
First lets find the slope through the points (\"1\",\"2\") and (\"-3\",\"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 (\"1\",\"2\") and (\"x%5B2%5D\",\"y%5B2%5D\") is the second point (\"-3\",\"5\"))
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\n" ); document.write( " \"m=%285-2%29%2F%28-3-1%29\" Plug in \"y%5B2%5D=5\",\"y%5B1%5D=2\",\"x%5B2%5D=-3\",\"x%5B1%5D=1\" (these are the coordinates of given points)
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\n" ); document.write( " \"m=+3%2F-4\" Subtract the terms in the numerator \"5-2\" to get \"3\". Subtract the terms in the denominator \"-3-1\" to get \"-4\"
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\n" ); document.write( " \"m=-3%2F4\" Reduce
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\n" ); document.write( " So the slope is
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\n" ); document.write( " \"m=-3%2F4\"
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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-2=%28-3%2F4%29%28x-1%29\" Plug in \"m=-3%2F4\", \"x%5B1%5D=1\", and \"y%5B1%5D=2\" (these values are given)
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\n" ); document.write( " \"y-2=%28-3%2F4%29x%2B%28-3%2F4%29%28-1%29\" Distribute \"-3%2F4\"
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\n" ); document.write( " \"y-2=%28-3%2F4%29x%2B3%2F4\" Multiply \"-3%2F4\" and \"-1\" to get \"3%2F4\"
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\n" ); document.write( " \"y=%28-3%2F4%29x%2B3%2F4%2B2\" Add \"2\" to both sides to isolate y
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\n" ); document.write( " \"y=%28-3%2F4%29x%2B11%2F4\" Combine like terms \"3%2F4\" and \"2\" to get \"11%2F4\" (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 (\"1\",\"2\") and (\"-3\",\"5\") is:\"y=%28-3%2F4%29x%2B11%2F4\"
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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%2F4\" and the y-intercept is \"b=11%2F4\"
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\n" ); document.write( " Notice if we graph the equation \"y=%28-3%2F4%29x%2B11%2F4\" and plot the points (\"1\",\"2\") and (\"-3\",\"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=%28-3%2F4%29x%2B11%2F4\" through the points (\"1\",\"2\") and (\"-3\",\"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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Solved by pluggable solver: Finding the Equation of a Line Parallel or Perpendicular to a Given Line

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\n" ); document.write( " Remember, any two perpendicular lines are negative reciprocals of each other. So if you're given the slope of \"-3%2F4\", you can find the perpendicular slope by this formula:
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\n" ); document.write( " \"m%5Bp%5D=-1%2Fm\" where \"m%5Bp%5D\" is the perpendicular slope
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\n" ); document.write( " \"m%5Bp%5D=-1%2F%28-3%2F4%29\" So plug in the given slope to find the perpendicular slope
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\n" ); document.write( " \"m%5Bp%5D=%28-1%2F1%29%284%2F-3%29\" When you divide fractions, you multiply the first fraction (which is really \"1%2F1\") by the reciprocal of the second
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\n" ); document.write( " \"m%5Bp%5D=4%2F3\" Multiply the fractions.
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\n" ); document.write( " So the perpendicular slope is \"4%2F3\"
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\n" ); document.write( " So now we know the slope of the unknown line is \"4%2F3\" (its the negative reciprocal of \"-3%2F4\" from the line \"y=%28-3%2F4%29%2Ax%2B11%2F4\").\n" ); document.write( "Also since the unknown line goes through (1,2), we can find the equation by plugging in this info into the point-slope formula
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\n" ); document.write( " Point-Slope Formula:
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\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 the given point
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\n" ); document.write( " \"y-2=%284%2F3%29%2A%28x-1%29\" Plug in \"m=4%2F3\", \"x%5B1%5D=1\", and \"y%5B1%5D=2\"
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\n" ); document.write( " \"y-2=%284%2F3%29%2Ax-%284%2F3%29%281%29\" Distribute \"4%2F3\"
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\n" ); document.write( " \"y-2=%284%2F3%29%2Ax-4%2F3\" Multiply
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\n" ); document.write( " \"y=%284%2F3%29%2Ax-4%2F3%2B2\"Add \"2\" to both sides to isolate y
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\n" ); document.write( " \"y=%284%2F3%29%2Ax-4%2F3%2B6%2F3\" Make into equivalent fractions with equal denominators
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\n" ); document.write( " \"y=%284%2F3%29%2Ax%2B2%2F3\" Combine the fractions
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\n" ); document.write( " \"y=%284%2F3%29%2Ax%2B2%2F3\" Reduce any fractions
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\n" ); document.write( " So the equation of the line that is perpendicular to \"y=%28-3%2F4%29%2Ax%2B11%2F4\" and goes through (\"1\",\"2\") is \"y=%284%2F3%29%2Ax%2B2%2F3\"
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\n" ); document.write( " So here are the graphs of the equations \"y=%28-3%2F4%29%2Ax%2B11%2F4\" and \"y=%284%2F3%29%2Ax%2B2%2F3\"
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\n" ); document.write( " graph of the given equation \"y=%28-3%2F4%29%2Ax%2B11%2F4\" (red) and graph of the line \"y=%284%2F3%29%2Ax%2B2%2F3\"(green) that is perpendicular to the given graph and goes through (\"1\",\"2\")
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\n" ); document.write( "Point of intersection (1,2) (this is given and is clearly visible)
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\n" ); document.write( "\"%28-3%2F4%29x%2B11%2F4=%284%2F3%29x%2B2%2F3\" Start with the given expression
\n" ); document.write( "\"%28-3%2F4%29x%2B11%2F4-2%2F3=%284%2F3%29x\" Subtract \"2%2F3\" from both sides
\n" ); document.write( "\"11%2F4-2%2F3=%284%2F3%29x%2B%283%2F4%29x\" Add \"%283%2F4%29x\" to both sides
\n" ); document.write( "\"25%2F12=%2825%2F12%29x\" Combine like terms
\n" ); document.write( "\"%2825%2F12%29%2812%2F25%29=x\" Multiply both sides by \"12%2F25\"
\n" ); document.write( "\"x=1\" Simplify
\n" ); document.write( "\"y=%284%2F3%291%2B2%2F3\" Plug in x=1
\n" ); document.write( "\"y=4%2F3%2B2%2F3\" Multiply
\n" ); document.write( "\"y=6%2F3\" Add
\n" ); document.write( "\"y=2\" Reduce
\n" ); document.write( "So the intersection is (1,2). This verifies our original answer.
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