document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=49042>Question 49042</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I have a graph plotted (7,5) and (8,3) , horizontal axis is D and vertical axis is P. i need to get the equation of the line joining these points, i.e) P= 1d - 2 but it isnt that and i cant work it out, any help would be appreciated.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #37348 by </B><A HREF=/tutors/aboutme.mpl?userid=rchill><B>rchill(405)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rchill><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=37348\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> If you have two points, you can determine the equation of a line in the form of y=mx+b, where m is the slope.  The slope, m, is defined as <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=m=%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29 ALIGN=MIDDLE  ALT=\"m=%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  It doesn't matter which ordered pair is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x%5B1%5D ALIGN=MIDDLE  ALT=\"x%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" >,<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y%5B1%5D ALIGN=MIDDLE  ALT=\"y%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > and <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x%5B2%5D ALIGN=MIDDLE  ALT=\"x%5B2%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" >,<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y%5B2%5D ALIGN=MIDDLE  ALT=\"y%5B2%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > because you'll get the same answer.  Using substitution we get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=m=%285-3%29%2F%287-8%29 ALIGN=MIDDLE  ALT=\"m=%285-3%29%2F%287-8%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > which reduces to m=-2.  So our formula so far is y=-2x+b.  To find out what b is, substitute one of your points (both x and y) into the equation; using the first ordered pair we get 5=-2*7+b, which simplifies to b=19.  So the equation is y=-2x+19.  Note that you'll get the exact same if you were to use the other ordered pair.<br><br>Because you need the equation with D and P instead of x and y, the formula becomes <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=P=-2D%2B19 ALIGN=MIDDLE  ALT=\"P=-2D%2B19\"   DISABLED_style= \"max-width:90%; height:auto;\" >. </SPAN>\n" );
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