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

side 1: 3x2 - 4x - 1
side 2: 4x - x2 + 5

the perimeter of the triangle is 5x3 - 2x2 + 3x - 8.

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.