The expression representing the height of the box is x+1.
The volume of the box is the product of length, breadth and width.
The volume of the box = l x b x h
x³ + 5x² -8x - 12 = (x + 6) . (x -2) .h
= (x²+ 4x -12) .h
h = (x³ + 5x² -8x - 12) / (x²+ 4x -12)
On dividing we get
h = x +1
Therefore, the expression representing the height of the box is x +1.
Learn more about volume of cuboid.
https://brainly.com/question/23118276
#SPJ1