document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=103742>Question 103742</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0030565111/algebrahomeworkh>Precalculus A GRAPHING APPROACH</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> My problem is to find the number c such that the vertex of f(x)=x^2+8x+c lies on the x-axis. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #75394 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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=75394\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> find the number c such that the vertex of f(x)=x^2+8x+c lies on the x-axis.<BR>\n" );
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document.write( "y-c = x^2+8x\r<BR>\n" );
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document.write( "Complete the square:\r<BR>\n" );
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document.write( "y-c+4^2 = x^2+8x+4^2<BR>\n" );
document.write( "(x+4)^2 = y-(c-16)<BR>\n" );
document.write( "The vertex is at (-4,c-16)<BR>\n" );
document.write( "If the vertex is going to be on the x-axis c-16 must be zero:<BR>\n" );
document.write( "c-16 = 0<BR>\n" );
document.write( "c = 16<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H. </SPAN>\n" );
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