Select the correct answer.

Two buildings on opposite sides of a highway are [tex]$3x^3 - x^2 + 7x + 100$[/tex] feet apart. One building is [tex]$2x^2 + 7x$[/tex] feet from the highway. The other building is [tex]$x^3 + 2x^2 - 18$[/tex] feet from the highway. What is the standard form of the polynomial representing the width of the highway between the two buildings?

A. [tex]2x^3 + x^2 + 7x + 118[/tex]

B. [tex]x^3 + 4x^2 + 7x - 18[/tex]

C. [tex]3x^3 - 3x^2 + 100[/tex]

D. [tex]2x^3 - 5x^2 + 118[/tex]



Answer :

To find the width of the highway between the two buildings, we need to follow these steps:

1. Expression for the distance between the buildings:
The total distance between the two buildings is given by the polynomial:
[tex]\[ 3x^3 - x^2 + 7x + 100 \][/tex]

2. Expression for the distance of Building 1 from the highway:
Building 1 is given to be [tex]\(2x^2 + 7x\)[/tex] feet from the highway:
[tex]\[ 2x^2 + 7x \][/tex]

3. Expression for the distance of Building 2 from the highway:
Building 2 is given to be [tex]\(x^3 + 2x^2 - 18\)[/tex] feet from the highway:
[tex]\[ x^3 + 2x^2 - 18 \][/tex]

4. Determine the total distance of both buildings combined from the highway:
By adding the distances of each building from the highway, we get:
[tex]\[ (2x^2 + 7x) + (x^3 + 2x^2 - 18) \][/tex]
This simplifies to:
[tex]\[ x^3 + 4x^2 + 7x - 18 \][/tex]

5. Subtraction to find the width of the highway:
The width of the highway is the total distance between the buildings minus the combined distances from the highway:
[tex]\[ (3x^3 - x^2 + 7x + 100) - (x^3 + 4x^2 + 7x - 18) \][/tex]

6. Simplification:
We subtract the polynomials:
[tex]\[ 3x^3 - x^2 + 7x + 100 - x^3 - 4x^2 - 7x + 18 \][/tex]

Combining like terms:
[tex]\[ (3x^3 - x^3) + (-x^2 - 4x^2) + (7x - 7x) + (100 + 18) \][/tex]
Simplifies to:
[tex]\[ 2x^3 - 5x^2 + 118 \][/tex]

Thus, the standard form of the polynomial representing the width of the highway is:
[tex]\[ \boxed{2x^3 - 5x^2 + 118} \][/tex]

Therefore, the correct answer is D.