Kenard takes a square piece of cardboard and cuts 4 in. by 4 in. squares...
I hope this helps. (:
Since original square has sides x,
when we cut 4 units from all the 4 sides the box will have height of 4 units.
Length of the box = side of square - 2 times square side cut
= x-2(4) = x-8
Similarly width of the box also would be
Hence volume of the box = lwh
= length x widthx height
Now substitute for each in terms of x
(3x-8) or (3x+8)