Question 1081905
If 8 is the old length, then 8-2x is the new length because we take x from both sides (there are 2 corner edges being cut off) to shrink down the length. 


Similarly, 6 is the old width and 6-2x is the new width.


x is the height


Volume = (length)*(width)*(height)
Volume = (8-2x)*(6-2x)*(x)


The closest choice is <font color=red>choice D</font> which is the answer. However, you aren't looking for the roots of this polynomial. Instead you're looking for the local max. So you shouldn't set the expression (8-2x)*(6-2x)*(x) equal to 0.