Explanation:
Given that,
A box is created from a sheet of cardboard 40in. on a side by cutting a square from each corner and folding up the sides.
Let x represent the length of the sides of squares removed from each corner.
(a) The volume of a cuboid is given by :
V = lbh
Put values,
V = x(40-2x)(40-2x)
(b) (40-2x) = -2(x-20)
So,
V = x(40-2x)(40-2x)
=
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(c)
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It is a cubic polynomial. Its degree is 3.