Get the answers you need from a community of experts on IDNLearn.com. Ask anything and receive thorough, reliable answers from our community of experienced professionals.

A rectangular prism with a volume of 400 cubic centimeters has dimensions [tex]x+1[/tex] centimeters, [tex]2x[/tex] centimeters, and [tex]x+6[/tex] centimeters. The equation [tex]2x^3+14x^2+12x=400[/tex] can be used to find [tex]x[/tex]. What is the length of the longest side? Use a graphing calculator and a system of equations to find the answer.

A. 4 centimeters
B. 5 centimeters
C. 8 centimeters
D. 10 centimeters


Sagot :

To solve for the value of [tex]\( x \)[/tex] and determine the length of the longest side of the rectangular prism, we need to follow these steps:

1. Set up the volume equation: Given the dimensions of the prism [tex]\( (x+1) \)[/tex] cm, [tex]\( (2x) \)[/tex] cm, and [tex]\( (x+6) \)[/tex] cm, we should start by setting up the volume equation. The volume [tex]\( V \)[/tex] is given by the product of these dimensions:
[tex]\[ V = (x + 1)(2x)(x + 6) \][/tex]
Given that the volume is 400 cubic centimeters, we write:
[tex]\[ (x + 1)(2x)(x + 6) = 400 \][/tex]

2. Expand and simplify: First, expand the left-hand side of the equation:
[tex]\[ (x + 1)(2x)(x + 6) = 2x(x^2 + 7x + 6) \][/tex]
[tex]\[ 2x(x^2 + 7x + 6) = 2x^3 + 14x^2 + 12x \][/tex]
Thus, the equation becomes:
[tex]\[ 2x^3 + 14x^2 + 12x = 400 \][/tex]

3. Set the equation to zero: Move all terms to one side of the equation to set it to zero:
[tex]\[ 2x^3 + 14x^2 + 12x - 400 = 0 \][/tex]

4. Solve the cubic equation: Use a graphing calculator or other appropriate numerical methods to find the roots of the equation [tex]\( 2x^3 + 14x^2 + 12x - 400 = 0 \)[/tex].

Using a graphing calculator:
- Plot the function [tex]\( f(x) = 2x^3 + 14x^2 + 12x - 400 \)[/tex].
- Identify the x-intercepts (roots) of this function.

After plotting, we find that one of the real roots is approximately [tex]\( x = 4 \)[/tex].

5. Calculate the dimensions: Substitute [tex]\( x = 4 \)[/tex] back into the original dimensions to find each side:
[tex]\[ \text{Side 1} = x + 1 = 4 + 1 = 5 \text{ cm} \][/tex]
[tex]\[ \text{Side 2} = 2x = 2(4) = 8 \text{ cm} \][/tex]
[tex]\[ \text{Side 3} = x + 6 = 4 + 6 = 10 \text{ cm} \][/tex]

6. Determine the longest side: Compare the calculated dimensions to find the longest side:
[tex]\[ \text{Side 1} = 5 \text{ cm}, \quad \text{Side 2} = 8 \text{ cm}, \quad \text{Side 3} = 10 \text{ cm} \][/tex]
The longest side is [tex]\( \text{Side 3} = 10 \text{ cm} \)[/tex].

Therefore, the length of the longest side is [tex]\(\boxed{10 \text{ centimeters}}\)[/tex].
Thank you for using this platform to share and learn. Don't hesitate to keep asking and answering. We value every contribution you make. IDNLearn.com has the solutions to your questions. Thanks for stopping by, and come back for more insightful information.