The lengths of two sides of a triangle are shown.
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? Show your work. (4 points)
Part B: What is the length of the third side of the triangle? Show your work. (4 points)
Part C: Do the answers for Part A and Part B show that the polynomials are closed under addition and subtraction?
Justify your answer. (2 points)