document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=499869>Question 499869</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I dont understand how to write an equation of the line that passes through (-2,1) and is perpindicular to y=1/2x+1.\r<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #337883 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=337883\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> y = 1/2x + 1 is an equation in y = mx + b form.<BR>\n" );
document.write( "This form is known as \"slope-intercept\" because m is the slope and b is the y-intercept.<BR>\n" );
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document.write( "The slope of a line perpendicular to this line will have slope = inverse reciprocal.<BR>\n" );
document.write( "The inverse reciprocal of 1/2 is -2.<BR>\n" );
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document.write( "So the line we're looking for is:<BR>\n" );
document.write( "y = -2x + b<BR>\n" );
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document.write( "It will run from the upper left corner of the graph to the lower right corner.<BR>\n" );
document.write( "The y value will be decreasing as the x value is increasing.<BR>\n" );
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document.write( "There are infinitely many lines with slope -2.<BR>\n" );
document.write( "But only one line with slope = -2 will go through the point (-2,1).<BR>\n" );
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document.write( "Notice that (-2,1) means that when x=-2, y=1.<BR>\n" );
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document.write( "We can plug that into the equation and find 'b'.<BR>\n" );
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document.write( "y = -2x + b<BR>\n" );
document.write( "1 = -2(-2) + b<BR>\n" );
document.write( "1 = 4 + b<BR>\n" );
document.write( "subtract 4 from both sides<BR>\n" );
document.write( "-3 = b<BR>\n" );
document.write( "so<BR>\n" );
document.write( "b = -3<BR>\n" );
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document.write( "That means the equation you need to find is:<BR>\n" );
document.write( "y = -2x -3<BR>\n" );
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document.write( "The following graphs show the two lines.<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=graph%28500%2C500%2C-5%2C5%2C-5%2C5%2C1%2F2%2Ax%2B1%2C-2%2Ax-3%29 ALIGN=MIDDLE  ALT=\"graph%28500%2C500%2C-5%2C5%2C-5%2C5%2C1%2F2%2Ax%2B1%2C-2%2Ax-3%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "Done. </SPAN>\n" );
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