document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=632691>Question 632691</A>: <I><SPAN STYLE=\"word-break: break-all;\"> find the vertex of y=(-1/4)x^2-(1/5)x </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #398419 by </B><A HREF=/tutors/aboutme.mpl?userid=dfrazzetto><B>dfrazzetto(283)</B></A><img src=\"/images/stars/stars-09.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=dfrazzetto><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=dfrazzetto><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=398419\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> coefficient of the x^2 term is negative, so it's an upside down parabola, vertex will be at the local maximum, which occurs when the derivative of y(x) = 0\r<BR>\n" );
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document.write( "y(x) = -x^2/4 - x/5\r<BR>\n" );
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document.write( "dy/dx (y(x)) = -x/2 - 1/5 \r<BR>\n" );
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document.write( "set equal to zero:\r<BR>\n" );
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document.write( "-x/2 - 1/5 = 0\r<BR>\n" );
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document.write( "-x/2 = 1/5\r<BR>\n" );
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document.write( "x = -2/5\r<BR>\n" );
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document.write( "The highest point on the upside down parabola, which is the vertex, occurs when x= -2/5\r<BR>\n" );
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document.write( "y(x) = -x^2/4 - x/5\r<BR>\n" );
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document.write( "y(-2/5) = (-1/4)(-2/5)^2  - (-2/5)/5\r<BR>\n" );
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document.write( " =   (-1/4)(4/25) + 2/25\r<BR>\n" );
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document.write( " =  -1/25 + 2/25 = 1/25\r<BR>\n" );
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document.write( "x = -2/5, y = 1/25\r<BR>\n" );
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document.write( "(-2/5, 1/25) </SPAN>\n" );
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