document.write( "Question 1109709: Form quadratic functions given the following information:
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\n" ); document.write( "\n" ); document.write( "f(3+ sqrt2 )=f(3−sqrt2 )=0; f(1)=−8
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Algebra.Com's Answer #724797 by greenestamps(13200)\"\" \"About 
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\n" ); document.write( "The roots are 3+sqrt(2) and 3-sqrt(2); that means the axis of symmetry is x=3; that means the vertex has x coordinate 3. Then the vertex form of the equation is

\n" ); document.write( "\"y+=+a%28x-3%29%5E2+%2B+k\"

\n" ); document.write( "Then since y is 0 when x is 3+sqrt(2),
\n" ); document.write( "\"0+=+a%28sqrt%282%29%29%5E2%2Bk\"
\n" ); document.write( "\"0+=+2a%2Bk\" (1)

\n" ); document.write( "And since y is -8 when x is 1,
\n" ); document.write( "\"-8+=+a%28-2%29%5E2%2Bk\"
\n" ); document.write( "\"-8+=+4a%2Bk\" (2)

\n" ); document.write( "Then from equations (1) and (2)

\n" ); document.write( "\"-8+=+2a\"
\n" ); document.write( "\"a+=+-4\"

\n" ); document.write( "And then from either equation (1) or (2), k = 8.

\n" ); document.write( "So the equation is

\n" ); document.write( "\"y+=+-4%28x-3%29%5E2%2B8\"
\n" ); document.write( "\"y+=+-4%28x%5E2-6x%2B9%29%2B8\"
\n" ); document.write( "\"y+=+-4x%5E2%2B24x-28\"

\n" ); document.write( "Solving this equation using the quadratic formula verifies that the roots are 3 +/- sqrt(2); evaluating the expression for x=1 verifies that the y value is -8.
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