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Mathematics 9 Online
OpenStudy (babynini):

Local max and min question!

zepdrix (zepdrix):

Ahhh she's back! Just couldn't stay away from the ole O'Study could ya?

OpenStudy (babynini):

haha i'm surprised you are brave enough to tackle another one of my questions!

zepdrix (zepdrix):

That's a terrible nickname, O'study..? Pretend I didn't say that...

OpenStudy (babynini):

xD although it is not allowing me to attach a file. sigh.

zepdrix (zepdrix):

Hmm site been really laggy today :[

OpenStudy (babynini):

Gah. well..it's 4x^3+3x^2-6x+8 local max? local min?

OpenStudy (babynini):

I got that the critical points are -1 and 1/4 but that is not working for the max and min?

zepdrix (zepdrix):

A polynomial?? Come on Mare.. you can do this one -_-

zepdrix (zepdrix):

hmm

zepdrix (zepdrix):

I think you get 1/2 for the positive critical point, ya? Maybe check your work again.

zepdrix (zepdrix):

\[\large\rm 4x^3+3x^2-6x+8\qquad D\to\qquad 12x^2+6x-6\]Looking for critical points,\[\large\rm 0=2x^2+x-1\]You can try to factor it, I think Quadratic Formula is easier from here though.

OpenStudy (babynini):

oh yes, I meant 1/2 not 1/4

zepdrix (zepdrix):

Oh :o

OpenStudy (babynini):

Critical points: -1, 1/2

zepdrix (zepdrix):

What'd you get for your extrema? -1 is the max, ya?

OpenStudy (babynini):

yes but it doesn't like that answer D:

OpenStudy (babynini):

oou because it's asking for locals maybe??

zepdrix (zepdrix):

Locals? Yes maybe. Did they give you a closed interval?

OpenStudy (babynini):

Nope

OpenStudy (babynini):

zepdrix (zepdrix):

Oh hehe.

zepdrix (zepdrix):

We found the `location of the local minimum`, ya? ;) Do you see what we didn't do?

OpenStudy (babynini):

uhm uhm. no haha what? D:

zepdrix (zepdrix):

We found the `local minimum LOCATION, x=1/2`, they want us to go a step further and give the `local minimum VALUE`.

OpenStudy (babynini):

ou. so we want to put those into the original function?

zepdrix (zepdrix):

Yes. That will give us VALUES for our min and max.

OpenStudy (babynini):

so for -1 = 13 1/2 = 25/4 ?

zepdrix (zepdrix):

Yes, good job.

OpenStudy (babynini):

Excellent, thank you! :)

zepdrix (zepdrix):

np

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