document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=42917>Question 42917</A>: <I><SPAN STYLE=\"word-break: break-all;\"> what is the equation of the ellipse with foci at (0,-4)and (0,4)and the sum of its focal radii being 10 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #27981 by </B><A HREF=/tutors/aboutme.mpl?userid=fractalier><B>fractalier(6550)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=fractalier><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=fractalier><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=27981\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> If the sum of the focal radii is 10, we know b = 5.  And if the foci are at (0, ±4), we know c = 4.  Then a^2 = b^2 - c^2 = 25 - 16 = 9 and a = 3.<BR>\n" );
document.write( "Thus our equation is<BR>\n" );
document.write( "x^2 / 9 + y^2 / 25 = 1 </SPAN>\n" );
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