document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=283485>Question 283485</A>: <I><SPAN STYLE=\"word-break: break-all;\"> find the equation of the line that passes through (4,-3) and (8,-5) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #205759 by </B><A HREF=/tutors/aboutme.mpl?userid=oberobic><B>oberobic(2304)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=oberobic><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=205759\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> We are seeking an equation for a line that will go through the points (4,-3) and (8,-5).<BR>\n" );
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document.write( "We know the slope-intercept form of the equation is:  y = mx+b<BR>\n" );
document.write( "m = slope<BR>\n" );
document.write( "b = y-intercept<BR>\n" );
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document.write( "m = rise / run = change in y / change in x<BR>\n" );
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document.write( "m = (y<sub>2</sub>-y<sub>1</sub>)/(x<sub>2</sub>-x<sub>1</sub>)<BR>\n" );
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document.write( "(4,-3) = (x<sub>1</sub>,y<sub>1</sub>)<BR>\n" );
document.write( "(8,-5) = (x<sub>2</sub>,y<sub>2</sub>)<BR>\n" );
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document.write( "m = (-5 -(-3)) / (8 -4) = (-5 +3) / (8 -4) = -2/4 = -1/2<BR>\n" );
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document.write( "y = -1/2x + b<BR>\n" );
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document.write( "Now we can substitute what we know to find 'b'.<BR>\n" );
document.write( "For example, one of the points is (4,-3).<BR>\n" );
document.write( "Substituting for x and y...<BR>\n" );
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document.write( "-3 = -1/2(4) + b<BR>\n" );
document.write( "-3 = -2 + b<BR>\n" );
document.write( "-1 = b<BR>\n" );
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document.write( "And we know the other point is (8,-5)<BR>\n" );
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document.write( "-5 = -1/2(8) + b<BR>\n" );
document.write( "-5 = -4 + b<BR>\n" );
document.write( "-1 = b<BR>\n" );
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document.write( "b = -1 = y-intercept = (0,-1)<BR>\n" );
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document.write( "y = -1/2x -1<BR>\n" );
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document.write( "Another useful point to find is the x-intercept, which is where y=0.<BR>\n" );
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document.write( "0 = -1/2x -1<BR>\n" );
document.write( "1/2x = -1<BR>\n" );
document.write( "x = -2<BR>\n" );
document.write( "(-2,0)<BR>\n" );
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document.write( "Graph to check<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=graph%28500%2C500%2C-10%2C10%2C-10%2C10%2C-1%2F2%2Ax-1%29 ALIGN=MIDDLE  ALT=\"graph%28500%2C500%2C-10%2C10%2C-10%2C10%2C-1%2F2%2Ax-1%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "Answer:<BR>\n" );
document.write( "The equation is <BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y+=+-%281%2F2%29x+-1+=+-x%2F2+-1 ALIGN=MIDDLE  ALT=\"y+=+-%281%2F2%29x+-1+=+-x%2F2+-1\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "Done </SPAN>\n" );
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