document.write( "Question 428168: Find the maximum value of the function: y=-x^2+8x-4 \n" ); document.write( "
Algebra.Com's Answer #297677 by nerdybill(7384)\"\" \"About 
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y=-x^2+8x-4
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\n" ); document.write( "Since the coefficient associated with the x^2 is negative -- we know it is a parabola that opens downwards -- the vertex is then the max.
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\n" ); document.write( "value of x at max is:
\n" ); document.write( "x = -b/(2a)
\n" ); document.write( "x = -8/(2*(-1))
\n" ); document.write( "x = -8/(-2)
\n" ); document.write( "x = 4
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\n" ); document.write( "plug above back into:
\n" ); document.write( "y=-x^2+8x-4
\n" ); document.write( "y=-(4)^2+8(4)-4
\n" ); document.write( "y=-(16)+32-4
\n" ); document.write( "y=-16+32-4
\n" ); document.write( "y = 12 (max value of y)\r
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