document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=540859>Question 540859</A>: <I><SPAN STYLE=\"word-break: break-all;\"> a parabola passes through the points (0,8),(2,-1) and (4,-1). find the equation of the parabola.\r<BR>\n" );
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document.write( "thanks  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #354018 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=354018\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> a parabola passes through the points (0,8),(2,-1) and (4,-1).<BR>\n" );
document.write( " find the equation of the parabola.<BR>\n" );
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document.write( "Using the form ax^2 + bx + c = y<BR>\n" );
document.write( "The first point, 0,8, indicates that c = 8<BR>\n" );
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document.write( "Write equations for the other two points<BR>\n" );
document.write( "x=2, y=-1<BR>\n" );
document.write( "4a + 2b + 8 = -1<BR>\n" );
document.write( "4a + 2b = -1 -8<BR>\n" );
document.write( "4a + 2b = -9<BR>\n" );
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document.write( "x=4, y=-1<BR>\n" );
document.write( "16a + 4b + 8 = -1<BR>\n" );
document.write( "16a + 4b = -9<BR>\n" );
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document.write( "multiply the 1st equation by -2, add to the 2nd equation<BR>\n" );
document.write( "-8a - 4b = +18<BR>\n" );
document.write( "16a + 4b = -9<BR>\n" );
document.write( "---------------adding eliminates b, find a<BR>\n" );
document.write( "8a = 9<BR>\n" );
document.write( "a = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=9%2F8 ALIGN=MIDDLE  ALT=\"9%2F8\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "a = 1.125<BR>\n" );
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document.write( "Find b <BR>\n" );
document.write( "4a + 2b = -9<BR>\n" );
document.write( "4(1.125) + 2b = -9<BR>\n" );
document.write( "4.5 + 2b = -9<BR>\n" );
document.write( "2b = -9 - 4.5<BR>\n" );
document.write( "2b = -13.5<BR>\n" );
document.write( "b = -6.75<BR>\n" );
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document.write( "The equation: y = 1.125x^2 - 6.75x + 8<BR>\n" );
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document.write( "You can confirm this by substituting for x and finding y for each point </SPAN>\n" );
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