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Mathematics 11 Online
OpenStudy (anonymous):

Help again please! :) Let g(x) = integral of 0 to x f(t) dt, where f is the function whose graph is shown. Answer the following questions only on the interval [0,10]. 1) At what values of x does g have a local maximum? 2) At what values of x does g have a local minimum? 3) At what value of x does g have an absolute maximum?

OpenStudy (anonymous):

OpenStudy (anonymous):

And that is the graph of the function

ganeshie8 (ganeshie8):

\[g(x) = \int_0^x f(t) dt \] \[\implies g'(x) = f(x) \]

ganeshie8 (ganeshie8):

So basically you have the graph of derivative of \(g\), and u need to find max/min of \(g\)

ganeshie8 (ganeshie8):

Look at the graph, at what points the derivative graph is becoming 0 ?

OpenStudy (anonymous):

I put in x=1,5, and 9 but it didn't work

OpenStudy (anonymous):

the question is on an website of sorts but it won't accept it

OpenStudy (anonymous):

i meant x=1,5,9 for maximums

ganeshie8 (ganeshie8):

Nope they're not maximums

ganeshie8 (ganeshie8):

At local maximums of \(g\), the graph of \(f\) needs to be \(0\), and decreasing.

ganeshie8 (ganeshie8):

So, Local maximums occur at x = 2, 6, 10

ganeshie8 (ganeshie8):

try this and see if it works..

OpenStudy (anonymous):

yeah those worked. but i thought those were inflection points, why would they be the maxs and mins?

ganeshie8 (ganeshie8):

cuz you're not looking at funciton

ganeshie8 (ganeshie8):

you're looking at `derivative of a function`

ganeshie8 (ganeshie8):

whenever derivative equals 0, its a possible max/min point right ?

OpenStudy (anonymous):

ah right

ganeshie8 (ganeshie8):

see if u can figure out `local minimums`

OpenStudy (anonymous):

they would be at 0,4, and 8 because they are increasing and the derivative equals 0?

ganeshie8 (ganeshie8):

you got it !!

ganeshie8 (ganeshie8):

what about global/absolute maximum ?

OpenStudy (anonymous):

that would be x=10 since it has the largest peak out of the whole graph?

ganeshie8 (ganeshie8):

Excellent !!

ganeshie8 (ganeshie8):

just notice that the areas above and below x-axis almost eat eachother out till x = 8

ganeshie8 (ganeshie8):

and after that you got a huge peak of area, so x=10 is indeed the absolute maximum

OpenStudy (anonymous):

so just to clarify, the equation is g(x) = integral of 0 to x f(t) dt and the derivative of that is g'(x)= f(x), which is what the graph is because the derivative cancels out the antiderivative?

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