document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=211798>Question 211798</A>: <I><SPAN STYLE=\"word-break: break-all;\"> When graphing linear equations, why the line x=4 is a vertical line?<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 #160036 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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/cgi-bin/show-face.mpl?user=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=160036\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> the general form of the equaion of a straight line is:<BR>\n" );
document.write( "ax + by = c<BR>\n" );
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document.write( "a is the coefficient of the x term.<BR>\n" );
document.write( "b is the coefficient of the y term.<BR>\n" );
document.write( "c is the constant<BR>\n" );
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document.write( "the line will be vertical when b = 0<BR>\n" );
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document.write( "when b = 0, the y variable drops out of the equation and the equation becomes:<BR>\n" );
document.write( "ax = c<BR>\n" );
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document.write( "if you divide both sides of the equation by a, you get:<BR>\n" );
document.write( "x = c/a<BR>\n" );
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document.write( "you derive the slope intercept form of the straight line from the standard form of the straight line as follows:<BR>\n" );
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document.write( "ax + by = c <BR>\n" );
document.write( "subtract ax from both sides to get:<BR>\n" );
document.write( "by = -ax + c<BR>\n" );
document.write( "divide both sides by b to get:<BR>\n" );
document.write( "y = -ax/b + c/b<BR>\n" );
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document.write( "this can be written as:<BR>\n" );
document.write( "y = (-a/b)*x + (c/b)<BR>\n" );
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document.write( "the line is vertical when b = 0<BR>\n" );
document.write( "you can see that when the line is vertical, the slope is undefined and the y intercept is undefined.<BR>\n" );
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document.write( "a good website that addresses the standard equation of the line is found here:<BR>\n" );
document.write( "http://www.analyzemath.com/line/line.htm<BR>\n" );
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document.write( "they also have an interactive demonstration where you can vary the parameters of a, b, and c to see the effect on the line.<BR>\n" );
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document.write( "there are sliders to the left of the graph that you move to change the value of a, b, or c.<BR>\n" );
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