Question

HELP ASAP PLZ!!!!!!!
The length of two sides of a triangle are shown below:

Side 1: 3x^2-4x-1
Side 2: 4x-x^2+5

The perimeter of the triangle is 5x^3-2x^2+3x-8.

PART A: what is the total length of the sides, 1 and 2, of the triangle?

PART B: what is the length of the third side of the triangle?

PART C: do the answers for part A and Part B show that the polynomial are closed under addition and substitution? Justify your answer.