Answer
[tex] \boxed{x + 4}[/tex]
Option C is the correct option
Step by step explanation
Let's find the expression which represents the length of the box:
[tex] \mathsf{length \times width \times height \: of \: prism \: = \: volume \: of \: prism}[/tex]
[tex] \mathsf{lengh \times \: (x - 1) \times (x + 8) = {x}^{3} + 11 {x}^{2} + 20x - 32}[/tex]
[tex] \mathsf{length = \frac{ {x}^{3} + 11 {x}^{2} + 20x - 32 }{(x - 1)(x + 8)} }[/tex]
Write 11x² as a sum
[tex] \mathsf{ = \frac{ {x}^{3} - {x}^{2} + 12 {x}^{2} + 20x - 32 }{(x - 1)(x + 8)} }[/tex]
Write 20x as a sum
[tex] \mathsf{ = \frac{ {x}^{3} - {x}^{2} + 12 {x}^{2} - 12x + 32x - 32 }{(x - 1)(x + 8)}}[/tex]
Factor out x² from the expression
[tex] \mathsf{ = \frac{ {x}^{2}(x - 1) + 12 {x}^{2} - 12x + 32x - 32 }{(x - 1)(x + 8)} }[/tex]
Factor out 12 from the expression
[tex] \mathsf{ = \frac{ {x}^{2}(x - 1) + 12x(x - 1) + 32x - 32 }{(x - 1)(x + 8)} }[/tex]
Factor out 32 from the expression
[tex] \mathsf{ = \frac{ {x}^{2}(x - 1) + 12x(x - 1) + 32(x - 1) }{(x - 1)(x + 8)} }[/tex]
Factor out x+1 from the expression
[tex] \mathsf{ = \frac{(x - 1)( {x}^{2} + 12x + 32) }{(x - 1)(x + 8)} } [/tex]
Factor out 12x as a sum
[tex] \mathsf{ = \frac{(x - 1)( {x}^{2} + 8x + 4x + 32) }{(x - 1)(x + 8)} }[/tex]
Reduce the fraction with x-1
[tex] \mathsf{ = \frac{ {x}^{2} + 8x + 4x + 32 }{(x + 8)} }[/tex]
Factor out x from the expression
[tex] \mathsf{ = \frac{x(x + 8) + 4x + 32}{(x + 8)} }[/tex]
Factor out 4 from the expression
[tex] \mathsf{ = \frac{x(x + 8) + 4(x + 8)}{x + 8} }[/tex]
Factor out x+8 from the expression
[tex] \mathsf{ = \frac{(x + 8)(x + 4)}{x + 8} } [/tex]
Reduce the fraction with x+8
[tex] \mathsf{ = x + 4}[/tex]
hence, x+4 is the expression that represents the length of a box.
Hope I helped!
Best regards!
