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April 18, 2014

April 18, 2014

Posted by **Pd** on Tuesday, September 14, 2010 at 4:55am.

this is how far i have got with an answer

g'(x) = (2x-3) (sqrt(5+16x-4x^2) + 2sqrt(5+16x-4x^2)

= (-4x+16)(2x-2)/sqrt(5+16x-4x^2) + 2sqrt(5+16x-4x^2)

Simplify:

-2(8x^2-30x+7) / sqrt(-4x^2+16x+5)

Set this to 0:

0 = -2(8x^2-30x+7) / sqrt(-4x^2+16x+5)

0 = -2(8x^2-30x+7)

Factor:

0 = -2(2x-7)(4x-1)

Set each factor to 0:

2x-7 = 0, so x = 7/2

4x-1 = 0, so x = 1/4

can't work out how to get the xLEFT and xRIGHT to classify each using the first derivative to get local min or local max...

help!

- Math -
**Damon**, Tuesday, September 14, 2010 at 6:27amUse the second derivative. It it is positive at the stationary point the function is about to get bigger so that is a minimum. If it is negative, the function is about to get smaller so that is a maximum.

By the way I did not check what you did. I suspect it is right because you came out with reasonable points where the function is horizontal.

- Math -
**brian**, Wednesday, September 15, 2010 at 5:37amcall your tutor rather than trying to get someone else to do your course work for you

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