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)