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Mathematics 16 Online
OpenStudy (anonymous):

how do you find the maximum and minimum values of f(x)=x^3-6x^2-63x+2?

OpenStudy (anonymous):

you have to find the derivative. Get critical points and use those to get your max and min. and concavity and points of inflection are found with the 2nd derivative

OpenStudy (anonymous):

okay so I have two critical points, so how do i use those to get the max and min values?

OpenStudy (anonymous):

were you given an interval where the max and min values were to be found?

OpenStudy (anonymous):

because f(x) -> +-infinity for x->+-infinity

OpenStudy (anonymous):

To find all local maxima and local minima, compute the first derivative the given function and set it equal to 0, and solve for x.

OpenStudy (anonymous):

ya the interval is [-4,0]

OpenStudy (anonymous):

f'(x)=3x^2-12x-63

OpenStudy (anonymous):

putting f'(X)=0.we get

OpenStudy (anonymous):

x=7 and -3

OpenStudy (anonymous):

good, now check the f(x) values for those x's

OpenStudy (anonymous):

the highest one is your max and the lowest one is you min

OpenStudy (anonymous):

your*

OpenStudy (anonymous):

x=7 and x=-3.

OpenStudy (anonymous):

where does the given interval come in?

OpenStudy (anonymous):

if you didn't have an interval, then f(x) would not have a defined maximum and minimum, since it would just keep rising/falling as you increase/decrease x

OpenStudy (anonymous):

a function where this is not the case could be cos(x), which has its maximum at 1 and minimum at -1, without an interval. Try drawing the graphs, then you will see

OpenStudy (anonymous):

Please go through it.

OpenStudy (anonymous):

it looks good, except for the graph, it's not the right function

OpenStudy (anonymous):

|dw:1319784058815:dw|

OpenStudy (anonymous):

it should look something like that

OpenStudy (anonymous):

it should be quite clear that there are two local extrema

OpenStudy (anonymous):

Please see it.

OpenStudy (anonymous):

i mean, it should be quite from your graph

OpenStudy (anonymous):

perfect

OpenStudy (anonymous):

Thank you

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