The lengths of two sides of a triangle are shown below.
Side 1: 5x^2+2x-3
Side 2: 8x-3x^2+2
The perimeter of the triangle is: 2x^3-5x^2+4x-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.

Question

The lengths of two sides of a triangle are shown below.
Side 1: 5x^2+2x-3
Side 2: 8x-3x^2+2 
The perimeter of the triangle is: 2x^3-5x^2+4x-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.

xapproachesinfinity · Answer

The first you just add up the two lengths of the sides 
The second use the perimeter formula to find the 3 side

anonymous · Answer

I'm not good at adding polynomials, I get very confused!

anonymous · Answer

You think you could help me?

xapproachesinfinity · Answer

The 3 the polynomials are closed under addition and subtraction since if you add up polynomials you get other polynomial and the 1and 2 have proven that

anonymous · Answer

Okay thanks that helps part C! But I still am really bad at actually adding the equations up

xapproachesinfinity · Answer

I'm actually answering from my work haha using the phone

xapproachesinfinity · Answer

Wait for someone to provide extra help

anonymous · Answer

Okay thanks for help on C though!

xapproachesinfinity · Answer

You are welcome