Maxima - Minima Problems (1 Viewer)

cookiez69 · Jul 8, 2013

Hey guys,

I only need help with (c), can't seem to get it... Anyway thanks in advance.

HeroicPandas · Jul 8, 2013

"(c) Show that A is a maximum when half the wire fencing has been placed parallel to the brick wall"

(i've helped a human with this question on facebook, and that human sent me a photo of the question)

EDIT: damnnn whoever gave u that, editted the question

cookiez69 · Jul 8, 2013

Smile12345 said:
Can't see c.!

Whoops my bad! Here you go:

HeroicPandas · Jul 8, 2013

bit messy, making it look nice will waste time

$A = 98x - \frac{21x^2}{2} \\ \frac{dA}{dx} = 98 - 21x \\ $At $\frac{dA}{dx}=0,$ stationary points exist \\ \\98 - 21x = 0, x= $\frac{14}{3} \\ \\ $Test for max or min \\ $\frac{d^2A}{dx^2} = -21 \\ $Since $\frac{d^2A}{dx^2} <0, $then for all values of x when $\frac{dA}{dx} = 0,$ $$ are all max \\ ($$or sub in x = $\frac{14}{3}$ into $\frac{d^2A}{dx^2},$ $ $if u get a negative number its a max, if u get a positive number, its a min, in this case $\frac{d^2A}{dx^2 } $is always negative$$)$

Makematics · Jul 8, 2013

HeroicPandas said:
"(c) Show that A is a maximum when half the wire fencing has been placed parallel to the brick wall"

(i've helped a human with this question on facebook, and that human sent me a photo of the question)

EDIT: damnnn whoever gave u that, editted the question

are you saying we aren't humans

HeroicPandas · Jul 8, 2013

Makematics said:
are you saying we aren't humans

at night i feel weird... (its when i take a break from studying)

lochnessmonsta · Jul 8, 2013

Wouldnt you just get the marks if you found the derivative, then subbed in x=14/3 and showed that it equalled 0? And show second derivative is less than 0?

Edit: I see that you did that. I just found it wordy

Maxima - Minima Problems (1 Viewer)

cookiez69

What a stupid name, Nat.

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What a stupid name, Nat.

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