document.write( "Question 280076: f(x)=8x-3x^2 i must indicate if it has a maximum or minimum. how do i go about this \n" ); document.write( "
Algebra.Com's Answer #203557 by dabanfield(803)\"\" \"About 
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f(x)=8x-3x^2 i must indicate if it has a maximum or minimum. how do i go about this
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\n" ); document.write( "\n" ); document.write( "We need to find the \"critical points\" by taking the first derivative of f and setting that equal to zero:\r
\n" ); document.write( "\n" ); document.write( "f'(x) = 8 - 6x
\n" ); document.write( "8 - 6x = 0
\n" ); document.write( "x = 4/3\r
\n" ); document.write( "\n" ); document.write( "So a max or min occurs at x = 4/3.\r
\n" ); document.write( "\n" ); document.write( "The second derivative test tells us if we have a max or min:\r
\n" ); document.write( "\n" ); document.write( "f''(x) = -6\r
\n" ); document.write( "\n" ); document.write( "Since f''(x) < 0 for all x including x = 4/3 we know x = 4/3 is where a maxiumm occurs. The actual value of the maximum is:\r
\n" ); document.write( "\n" ); document.write( "f(4/3) = 8*(4/3) - 3*(4/3)^2
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