document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=695678>Question 695678</A>: <I><SPAN STYLE=\"word-break: break-all;\"> find b if you happen to know the maximum y-value of the function y= -4x^2 + bx -1 is 21.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #428606 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=428606\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> find b if you happen to know the maximum y-value of the function <BR>\n" );
document.write( "y= -4x^2 + bx -1 is 21<BR>\n" );
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document.write( "Comment:<BR>\n" );
document.write( "Maximum occurs where x = -b/(2a) = -b/(-8) = b/8<BR>\n" );
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document.write( "Max = f(b/8) = -4(b/8)^2 + b(b/8) -1 = 21<BR>\n" );
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document.write( "-4(b^2/64) + b^2/8 = 22<BR>\n" );
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document.write( "-b^2/16 +2(b^2/16) = 22<BR>\n" );
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document.write( "-b^2 + 2b^2 = 16*22<BR>\n" );
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document.write( "b^2 = 16*22<BR>\n" );
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document.write( "b = 4*sqrt(22)<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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