document.write( "Question 358372: Find the coordinates of the vertexfor the parabola defined by the given quadraric funtion. f(x)= -x^2-2x+1 \n" ); document.write( "
Algebra.Com's Answer #255760 by josmiceli(19441)\"\" \"About 
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The vertex is half way between the 2 roots
\n" ); document.write( "\"f%28x%29+=+-x%5E2+-+2x+%2B+1\"
\n" ); document.write( "Set \"f%28x%29+=+0\"
\n" ); document.write( "\"+-x%5E2+-+2x+%2B+1+=+0\"
\n" ); document.write( "Using the quadratic formula:
\n" ); document.write( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
\n" ); document.write( "\"a+=+-1\"
\n" ); document.write( "\"b+=+-2\"
\n" ); document.write( "\"c+=+1\"
\n" ); document.write( "\"x+=+%28-%28-2%29+%2B-+sqrt%28+%28-2%29%5E2-4%2A%28-1%29%2A1+%29%29%2F%282%2A%28-1%29%29+\"
\n" ); document.write( "\"x+=+%282+%2B-+sqrt%28+4+%2B+4+%29%29%2F+-2%29+\"
\n" ); document.write( "\"x+=+%282+%2B-+sqrt%28+8+%29%29%2F+-2%29+\"
\n" ); document.write( "\"x+=+%282+%2B-+2%2Asqrt%28+2+%29%29%2F+-2%29+\"
\n" ); document.write( "\"x+=+-1+%2B+sqrt%282%29\"
\n" ); document.write( "and
\n" ); document.write( "\"x+=+-1+-+sqrt%282%29\"
\n" ); document.write( "\"x+=+-1\" is half way between these 2 roots
\n" ); document.write( "Actually, this equals \"-b%2F%282a%29\" and
\n" ); document.write( "\"-b%2F%282a%29+=+-%28-2%29%2F%282%2A%28-1%29%29\"
\n" ); document.write( "\"+-%28-2%29%2F%282%2A%28-1%29%29+=+-1\"
\n" ); document.write( "Now plug \"x+=+-1\" into equation:
\n" ); document.write( "\"f%28x%29+=+-x%5E2+-+2x+%2B+1\"
\n" ); document.write( "\"f%28-1%29+=+-%28-1%29%5E2+-+2%2A%28-1%29+%2B+1\"
\n" ); document.write( "\"f%28-1%29+=+-1+%2B+2+%2B+1\"
\n" ); document.write( "\"f%28-1%29+=+2\"
\n" ); document.write( "The vertex is at (-1,2)
\n" ); document.write( "Here's a plot:
\n" ); document.write( "\"+graph%28+400%2C+400%2C+-5%2C+5%2C+-5%2C+5%2C+-x%5E2+-+2x+%2B+1%29+\"\r
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