The lengths of two sides of a triangle are shown below:

side 1: 8x^2 - 5x - 2
side 2: 7x - x^2 + 3
the perimeter of the triangle is 4x^3 - 3x^2 + 2x - 6

answer the following questions:
part a: what is the total length of the two 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 polynomials are closed under addition and subtraction? justify your answer.