document.write( "Question 43057: \"Graph the equation, then choose the correct coordinates of the foci. Keep the graphs as they may be asked for at a later time. y^2= 5x^2+25.\" I keep trying to graph equations like this and find the foci, but the answers I get are never one of the answer choices. For this one I did:
\n" ); document.write( "y^2= 5x^2+25
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\n" ); document.write( "y^2-5x^2= 25
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\n" ); document.write( "(y^2-5x^2)/-5=25/-5\r
\n" ); document.write( "\n" ); document.write( "-1/5(y^2/-5-x^2)=-5/-5
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\n" ); document.write( "y^2/25+x^2/5=1\r
\n" ); document.write( "\n" ); document.write( "y^2/(5)^2+x^2/(square root 5)^2=1\r
\n" ); document.write( "\n" ); document.write( "After that I had my x and y intercepts so I made my graph and tried to find the foci.\r
\n" ); document.write( "\n" ); document.write( "b^2=a^2-c^2\r
\n" ); document.write( "\n" ); document.write( "square root 5^2= 5^2-c^2\r
\n" ); document.write( "\n" ); document.write( "5= 25-c^2\r
\n" ); document.write( "\n" ); document.write( "5-25= -c^2\r
\n" ); document.write( "\n" ); document.write( "20= c^2\r
\n" ); document.write( "\n" ); document.write( "square root 20= c
\n" ); document.write( "I'd appreciate your help. These graphs have really been frustrating me. Please me know what I'm doing wrong. Thanx!
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Algebra.Com's Answer #28077 by psbhowmick(878)\"\" \"About 
You can put this solution on YOUR website!
\"y%5E2=+5x%5E2%2B25\"
\n" ); document.write( "or \"y%5E2-5x%5E2=+25\"
\n" ); document.write( "or \"%28y%5E2-5x%5E2%29%2F25=25%2F25%29\"
\n" ); document.write( "or \"y%5E2%2F25+-+x%5E2%2F5+=+1\"
\n" ); document.write( "or \"y%5E2%2F5%5E2+-+x%5E2%2F%28sqrt%285%29%29%5E2+=+1\"\r
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\n" ); document.write( "\n" ); document.write( "As simple as that!
\n" ); document.write( "Don't make the algebra complex.
\n" ); document.write( "Divide both sides by 25 (to make the term on right side = 1).
\n" ); document.write( "This is a hyperbola and not an ellipse.
\n" ); document.write( "You derived a wrong equation resulting in wrong type of conic (you got ellipse).\r
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\n" ); document.write( "\n" ); document.write( "Comparing with standard equation of hyperbola
\n" ); document.write( "\"y%5E2%2Fa%5E2+-+x%5E2%2Fb%5E2+=+1\"
\n" ); document.write( "where '2a' and '2b' are the lengths of transverse and conjugate axes respectively we have
\n" ); document.write( "a = 5, b = \"sqrt%285%29\"\r
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\n" ); document.write( "\n" ); document.write( "Now, eccentricity is \"e=sqrt%281+%2B+b%5E2%2Fa%5E2%29\"
\n" ); document.write( "or \"e=sqrt%281+%2B+5%2F5%5E2%29\"
\n" ); document.write( "or \"e=sqrt%281+%2B+1%2F5%29\"
\n" ); document.write( "or \"e=sqrt%286%2F5%29\"\r
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\n" ); document.write( "\n" ); document.write( "The foci are at (0,ae) and (0,-ae) i.e. (0,\"5sqrt%286%2F5%29\") and (0,\"-5sqrt%286%2F5%29\") i.e. (0,\"sqrt%2830%29\") and (0,\"-sqrt%2830%29\").\r
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