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Mathematics 16 Online
OpenStudy (anonymous):

Help, question below

OpenStudy (anonymous):

The function f(x) = 2 x^3 - 30 x^2 + 96 x + 9 has one local minimum and one local maximum. This function has a local minimum at x equals______ with value_______ and a local maximum at x_______ equals with value______

OpenStudy (anonymous):

@ranga help

OpenStudy (ranga):

will be abck soon. answering another question now.

OpenStudy (anonymous):

okay, and i got -96 for min and -6 for max, but it says it's wrong

OpenStudy (ranga):

What are the x values of your minimum and maximum?

OpenStudy (anonymous):

-96 and -6, but idk if it's right

OpenStudy (ranga):

Not the f(x) value but I was asking for the x value that you got for the critical points.

OpenStudy (anonymous):

the derivative for the function 6x^2 -60x+96, but i find it hard to find the critical numbers

OpenStudy (ranga):

Factor out 6 and throw it away. 6x^2 -60x+96 = 0 6(x^2 - 10x + 16) = 0 x^2 - 10x + 16 = 0 x^2 -8x - 2x + 16 = 0 x(x - 8) - 2(x - 8) = 0 (x-8)(x-2) = 0 x =2 or x = 8 Put these two values in f(x) and find f(2) and f(8)

OpenStudy (anonymous):

so the 8 is min and 2 is max

OpenStudy (anonymous):

so would the values be 0?

OpenStudy (ranga):

8 is the x value where minimum occurs. But that is not the minimum value of the function. For that you have to find f(8) 2 is the x value where maximum occurs. But that is not the maximum value of the function. For that you have to find f(2)

OpenStudy (ranga):

No. Don't put the x values of 2 and 8 in the derivative. Put it in the original function f(x)

OpenStudy (anonymous):

157, 1033

OpenStudy (ranga):

Nope. f(x) = 2 x^3 - 30 x^2 + 96 x + 9 f(2) = 2(2^3) - 30(2^2) + 96(2) + 9 = ? f(8) = 2(8^3) - 30(8^2) + 96(8) + 9 = ?

OpenStudy (anonymous):

97, -119

OpenStudy (anonymous):

Thanks

OpenStudy (anonymous):

how do u find the critical # for a f(x) = 6x+4x^-1.. the negative one thing set me off track

OpenStudy (ranga):

97 and -119 are correct. So the answer should be: This function has a local minimum at x equals___2___ with value__97_____ and a local maximum at x__8_____ equals with value__-119____

OpenStudy (anonymous):

Thanks

OpenStudy (ranga):

f(x) = 6x+4x^-1 What is the derivative. Use the power rule for x^-1

OpenStudy (anonymous):

would be 6-4x^-2 or 6-4x^-1*(-2)?

OpenStudy (ranga):

It is 6-4x^-2

OpenStudy (anonymous):

so how do i find the critical # after that, im just not good at finding critical #s?

OpenStudy (ranga):

Set the derivative to zero. drop the x^-2 to denominator so it becomes 1/x^2 6 - 4/x^2 = 0 solve for x

OpenStudy (anonymous):

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