Question 67627
1) An open-top box is to be constructed from a 4 foot by 6 foot rectangular cardboard by cutting out equal squares at each corner and the folding up the flaps. Let x denote the length of each side of the square to be cut out.
:
a) Find the function V that represents the volume of the box in terms of x.
Answer:
The dimensions of the box will be (4-2x) by (6-2x) by x
:
FOIL (4-2x)(6-2x) and you have: 24 - 20x + 4x^2, mult that x,
:
V(x) = 4x^3 - 20x^2 + 24x
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b) Graph this function and show the graph over the valid range of the variable x..
Show Graph here.
{{{ graph( 300, 200, -2, 3, -4, 10, 4x^3 - 20x^2 + 24x) }}}



c) Using the graph, what is the value of x that will produce the maximum volume?
Answer.
It looks like that about x =.75 ft will produce max volume (8.4 cu ft)
:
You can find out exactly for x = .75: (4-1.5) * (6-1.5) * .75 = 8.4375
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My Ti83 gave the max at x = .78475 produces a max vol of 8.45 cu ft
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