I am so confused on part C. Can someone please help me??

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? (4 points)

Part B: What is the length of the third side of the triangle? (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)

Question

I am so confused on part C. Can someone please help me??

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? (4 points)

Part B: What is the length of the third side of the triangle? (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)

anonymous · Answer

Part A wants to know the total length of the two sides. You need to add side 1 and side 2. You know how to add polynomials?

3x^2 - 4x - 1 + -x^2 + 4x  + 5

anonymous · Answer

I've already solved Part A and B

anonymous · Answer

Good, so what does your books say about closed sets?

anonymous · Answer

Good link for you to understand polynomials are closed https://learnzillion.com/lessons/2568-determine-whether-a-set-is-closed-or-open

anonymous · Answer

Sorry wrong link This is the right one https://learnzillion.com/lessons/2694-understand-that-polynomials-are-closed-under-addition-add-polynomials

anonymous · Answer

Here is one for subtraction https://learnzillion.com/lessons/2608-understand-that-polynomials-are-closed-under-subtraction-subtract-polynomials

anonymous · Answer

They will help you answer C

anonymous · Answer

Thank you

anonymous · Answer

YW