document.write( "Question 889601: find the equation of the parabola with vertex on the line y=x, the axis of parabola is parallel to the x-axis and passing through (6,-2)and (3,4)
\n" ); document.write( "
\n" ); document.write( "

Algebra.Com's Answer #538381 by josgarithmetic(39627)\"\" \"About 
You can put this solution on YOUR website!
\"highlight_green%28x=a%28y-k%29%5E2%2Bh%29\", parabola parallel to the horizontal axis.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "The line y=x containing the vertex means that the two coordinates of this point are equal in value.
\n" ); document.write( "Call this vertex (n,n).
\n" ); document.write( "The equation of the parabola can be expressed, \"highlight_green%28x=a%28y-n%29%5E2%2Bn%29\".\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "The variables, once the given points are substituted, will be a and n. General form should give
\n" ); document.write( "a system of equations which we could solve for a and n.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=a%28y%5E2-2yn%2Bn%5E2%29%2Bn\"
\n" ); document.write( "\"x=ay%5E2-2ayn%2Ban%5E2%2Bn\"
\n" ); document.write( "\"ay%5E2-2ayn%2Ban%5E2%2Bn-x=0\"
\n" ); document.write( "-
\n" ); document.write( "Maybe alternatively
\n" ); document.write( "\"a%28y%5E2-2yn%2Bn%5E2%29=x-n\"
\n" ); document.write( "\"a=%28x-n%29%2F%28y%5E2-2yn%2Bn%5E2%29\", because this gives a on one side and an expression in terms of n on the other side.
\n" ); document.write( "Knowing that a and n are constants, any point on the parabola should give equal expressions for the member on
\n" ); document.write( "the right-side.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Using the two given points, those points (6,-2) and (3,4),
\n" ); document.write( "\"a=%286-n%29%2F%28%28-2%29%5E2-2%28-2%29n%2Bn%5E2%29\"
\n" ); document.write( "and
\n" ); document.write( "\"a=%283-n%29%2F%284%5E2-2%2A4%2Bn%5E2%29\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "The two expressions for a must be equal.
\n" ); document.write( "\"%286-n%29%2F%28%28-2%29%5E2-2%28-2%29n%2Bn%5E2%29=%283-n%29%2F%284%5E2-2%2A4%2Bn%5E2%29\"
\n" ); document.write( "\"%286-n%29%2F%284%2B4n%2Bn%5E2%29=%283-n%29%2F%2816-8n%2Bn%5E2%29\"
\n" ); document.write( "\"%286-n%29%2816-8n%2Bn%5E2%29=%283-n%29%284%2B4n%2Bn%5E2%29\"
\n" ); document.write( "\"96-48n%2B6n%5E2-16n%2B8n%5E2-n%5E3=12%2B12n%2B3n%5E2-4n-4n%5E2-n%5E3\"
\n" ); document.write( "\"96-48n-16n%2B6n%5E2%2B8n%5E2=12%2B12n-4n%2B3n%5E2-4n%5E2\"
\n" ); document.write( "\"96-64n%2B14n%5E2=12%2B8n-n%5E2\"
\n" ); document.write( "\"96-12-64n-8n%2B14n%5E2%2Bn%5E2=0\"
\n" ); document.write( "\"15n%5E2-72n%2B84=0\", Divide this by 3;
\n" ); document.write( "\"highlight_green%285n%5E2-24n%2B28=0%29\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "How is the discriminant?
\n" ); document.write( "\"24%5E2-4%2A5%2A28\"
\n" ); document.write( "\"576-20%2A28\"
\n" ); document.write( "\"576-560\"
\n" ); document.write( "\"highlight_green%2816%29\", a perfect square whole number.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now, what can be n?
\n" ); document.write( "\"n=%2824%2B-+sqrt%2816%29%29%2F%282%2A5%29\"
\n" ); document.write( "\"n=%2824%2B-+4%29%2F10\"
\n" ); document.write( "Either \"highlight%28n=2%29\" Or \"highlight%28n=14%2F5%29\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "... Still not finished. We want to use these values for n to get our value for a; probably a single (or maybe not) value. You will have to try each of the solutions for n and find out.
\n" ); document.write( "
\n" ); document.write( "
\n" );