document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=970630>Question 970630</A>: <I><SPAN STYLE=\"word-break: break-all;\"> An arch that supports a bridge is built in the shape of a downwards opening parabola. Its span is 100 ft and max height is 8 ft. Find the equation of the parabola that models the situation. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #593323 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=593323\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> An arch that supports a bridge is built in the shape of a downwards opening parabola. Its span is 100 ft and max height is 8 ft.<BR>\n" );
document.write( " Find the equation of the parabola that models the situation.<BR>\n" );
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document.write( "Using the form y = ax^2 + bx + c<BR>\n" );
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document.write( "Let axis of symmetry x=0, and the y intercept is the max height of 8 ft.<BR>\n" );
document.write( "x intercept be -50 and +50; c = 8<BR>\n" );
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document.write( "x = -50, y = 0<BR>\n" );
document.write( "-50^2*a - 50b + 8 = 0<BR>\n" );
document.write( "2500a - 50b + 8 = 0<BR>\n" );
document.write( "and x=+50; y=0<BR>\n" );
document.write( "+50^2*a + 50b + 8 = 0<BR>\n" );
document.write( "2500a + 50b + 8 = 0<BR>\n" );
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document.write( "use elimination<BR>\n" );
document.write( "2500a - 50b + 8 = 0<BR>\n" );
document.write( "2500a + 50b + 8 = 0<BR>\n" );
document.write( "----------------------Adding eliminates b<BR>\n" );
document.write( "5000a + 16 = 0<BR>\n" );
document.write( "a = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-16%2F5000 ALIGN=MIDDLE  ALT=\"-16%2F5000\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "a = -.0032<BR>\n" );
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document.write( "Equation: y = -.0032x^2 + 8<BR>\n" );
document.write( "looks like this<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+graph%28+300%2C+200%2C+-80%2C+80%2C+-4%2C+10%2C+-.0032x%5E2%2B8%29+ ALIGN=MIDDLE  ALT=\"+graph%28+300%2C+200%2C+-80%2C+80%2C+-4%2C+10%2C+-.0032x%5E2%2B8%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( " </SPAN>\n" );
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