Polynomials: Adding & Subtracting

Question

A rectangle has a length of x and a width of 

4x³ + 9 − x².

 Find the perimeter of the rectangle when the length is 

6 feet.

 

The polynomial that models the perimeter of the rectangle is 

?

 

The perimeter is 

 feet?

Answer 1

Length is x=6

width is 4x^3 - x^2 + 9 = 837

perimeter is 2*6 + 2* 837 = 1686

2x + 2(4x^3 - x^2 + 9) = 8x^3 - 2x^2 + 18 + 2x = 8x^3 - 2x^2 + 2x + 18 = P(x)

Note that for x=6, P(6) = 1686