A doctor who is treated a heart patient wants to presicribe medication to lowere the patients blood pressure. The body's reaction to this medication is a function of the dose admininistered. If the patient takes x milliters of the medication, his blood pressure should decrease by r=f(x) points where
f(x)=3x^2-1/3x^3
what values of x make sence for this function

- toxicsugar22

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- toxicsugar22

can u please help

- anonymous

Hmm.. I would say find the min value, and would that give you the x value? that would make the most sense?

- toxicsugar22

i got 9 and 0

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## More answers

- anonymous

Okay, Im not sure I understand the question, sorry o.O
Because at x=0 f(x) =0 as well. I believe. I don't think that helps in anyway. Sorry

- amistre64

y = 3x^2-1
------- this?
3x^3

- anonymous

Ohhh. I didn't realize that was division. haha

- anonymous

sorry, but i dont know enough to help you out

- toxicsugar22

amitre is that the answer

- amistre64

no thats a question about the problem :) is that the question at hand?

- anonymous

Any value greater than 0 would make sense. right..

- toxicsugar22

no its what values of x make sence for this function

- amistre64

i think we want the maximum for f(x) so that his blood pressure reduces the most right?

- amistre64

well, any values of x will work except for x=0

- anonymous

i think we are looking for domain
?

- amistre64

y = 3x^2-1
------- is this the function we are working with?
3x^3

- toxicsugar22

yes

- amistre64

then lets see where this function is increaseing and decreasing for x

- anonymous

Domain should be any value greater than 0. But I don't think its that simple.

- anonymous

no amistre has got it

- anonymous

nned function to be decreasing, or blood pressure is not decreasing

- amistre64

the 1st derivative is:
3x^3(2x) - 9x^2(3x^2-1)
-21x^4 +9x^2
-------------
9x^6

- amistre64

when the derivative is zero we get the highes and lowes of it;

- amistre64

-3x^2 (7x^2 -3) = 0 when x = 0 and...
sqrt(12)/14 = sqrt(3)/7 the only value here that makes sense is sqrt(3/7)

- amistre64

now is it a high or a low :) or an inflection point
is there an answer key for this to determine if we are doing it right :)

- toxicsugar22

no ther isnt

- amistre64

3x^2-1
-------
3x^3
3 sqrt.3/7^2-1
--------------
3 sqrt.3/7^3
-40/49
-------------- thats a negative number so id say its not going to be that point :)
9/49 (sqrt.3/7)

- amistre64

lets see what the roots are if any to this equation
when 3x^2-1 =0
3x^2 = 1
x^2 = 1/3
x = sqrt(1/3) = sqrt(3)/3 is a zero

- toxicsugar22

so that is the answer

- amistre64

0.577 is a root

- amistre64

dunno; still running tests in my head :)

- toxicsugar22

ok its okay

- toxicsugar22

can u help me with one more that is not realted to this

- toxicsugar22

pomblem

- toxicsugar22

please

- amistre64

http://www.wolframalpha.com/input/?i=%283x^2-1%29%2F%283x^3%29 is what we get for a graph

- amistre64

its only effective after x=sqrt(3)/3 and peaks at x=1

- toxicsugar22

ok but can u help with anot

- amistre64

i can try :)

- toxicsugar22

ok
it poynomials are u good at that

- amistre64

i can be at times lol

- toxicsugar22

Find the first three terms in asending powers. (Do not compute the entire product)
(1-2x^2-x^4)(4+x^2-2x^4)

- amistre64

4 -7x^2 -8x^4

- toxicsugar22

thats the answer

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