# Need help solving this equation (may be factoring)?

• Apr 17th 2012, 01:07 PM
Flurite
Need help solving this equation (may be factoring)?
Hi, in math class, we were assigned a challenge problem that has to do with finding the volume of a box. My function is:

f(x) = 4x3 - 88x2 + 480x

I found that the maximum value of this function is 768 (the maximum volume), but I want to know how to solve for `x`. This is what I have:
768 = 4x3 - 88x2 + 480x
192 = x3 - 22x2 + 120x

How would I continue to solve for `x`?
• Apr 17th 2012, 01:46 PM
a tutor
Re: Need help solving this equation (may be factoring)?
How did you get your answer of 768? It should actually be about 774 by the way.

• Apr 17th 2012, 01:48 PM
skeeter
Re: Need help solving this equation (may be factoring)?
Quote:

Originally Posted by Flurite
Hi, in math class, we were assigned a challenge problem that has to do with finding the volume of a box. My function is:

f(x) = 4x3 - 88x2 + 480x

I found that the maximum value of this function is 768 (the maximum volume), but I want to know how to solve for `x`. This is what I have:
768 = 4x3 - 88x2 + 480x
192 = x3 - 22x2 + 120x

How would I continue to solve for `x`?

how did you find that the maximum volume is 768?

I get approximately 774.
• Apr 17th 2012, 02:07 PM
Flurite
Re: Need help solving this equation (may be factoring)?
I used my graphing calculator, but then I just realized that decimals are involved too. All I need is the `x` value and I can't find that in my table.
• Apr 17th 2012, 02:42 PM
skeeter
Re: Need help solving this equation (may be factoring)?
graph the volume and find the maximum ... it will give you the max volume (y-value) and x-value where that maximum occurs.
• Apr 17th 2012, 02:45 PM
Flurite
Re: Need help solving this equation (may be factoring)?
Found out how to change the maximum and minimum values to shift where the graph is showing. Thanks all!