Recent content by 619snake

Homework Statement the weight of items produced by a production line is normally distributedwith a mean of 12 ounces and a standard deviation of 2 ounces. a. what is the probability that a randomly selected item will weight between 8 and 16 ounces? (DONE) b. what is the probability that a...

Homework Statement the weight of items produced by a production line is normally distributed with a mean of 12 ounces and a standard deviation of 2 ounces. Suppose that quality control requires the weight of items to be within 8 and 16 ounces. You select 7 items at random (each item is...

need help with this problem x~normal(mean= 12, stdev=2) item weight from 8 to 16 ounces i have a random sample of 7 items and need to find the probability that 3 of those items fulfill the weight each item is independent this is what i got at the moment z=(16-12)/(2) = 2 p(z<2)-p(z<-2)...

Thanks people, solved the problem :biggrin:

I'm here again bothering you, I have this problem, but have no idea about how to start the problem solving: Homework Statement The USPS will accept packages only if the length plus girth is no more than 108 inches. Assuming that the front face is square, what is the largest volume package...

yay! now i can sketch the graph!

so... what is left now is to try to simplify and evaluate the second derivative right? if I'm not mistaken, after simplifying, the derivative ends like this: f"(x)=(2x(x^2 + 27))/(x^2 - 9)^3

must ask, when the second derivative: the second part of the term (-2x)(x^2-9) doesn't get squared like this: "(-2x)(x^2-9)^2"?

ok without that thing i did, the derivative is like this: f"(x)=(-2x(x^(2)-9)^2)+(x^(2)-9)(4x^(3)-36x)/(x^(2)-9)^4

but why? i simplified already

im sorry about those signs errors now i have something like this, after correcting the errors f"(x)=(-2x+(x^(2)+9)(4x^(3)-36x))/(x^(2)-9)^2

well... i got something like this... hope I am not mistaken xD f"(x)= ((-2x(x^(2)-9)^2)+(x^(2)-9)(4x^(3)-36x))/(x^(8)-36x^(6)+486^(4)-2916x^(2)+6561)

Yes I need to do concavity... it is a bit weird... because the second derivative is pretty long, and have really big numbers

ok the others are f'(x) < 0 (-\infty,-3), (3,\infty) I guess it's because of the asymptotes :rolleyes: :confused:

ok, if I'm not mistaken, f'(x) < 0 (-3,3)