How do I write a polynomial expression to represent the third side of the triangle? I know one side is 2x-3y and the other is x+2y and P=5x+2y? I am lost.

I will assume that P represents the perimeter.

Let the third side be S

S + 2x-3y + x+2y = 5x + 2y
S = 5x+2y - 2x + 3y - x - 2y
= 2x + 3y

check:
What is the sum of (x+2y) + (2x-3y) + (2x+3y) ??

To find the polynomial expression for the third side of the triangle, we can use the fact that the perimeter of a triangle is the sum of the lengths of its three sides.

Given that one side of the triangle is 2x - 3y and the other side is x + 2y, we can write the equation for the perimeter (P) as:

P = (2x - 3y) + (x + 2y) + S,

where S is the third side of the triangle that we're trying to find.

We also know that P = 5x + 2y, according to the information given.

Now, let's rearrange the equation to solve for S:

5x + 2y = (2x - 3y) + (x + 2y) + S

Combining like terms on the right side:

5x + 2y = 3x - y + S

To isolate S, move 3x and -y to the left side of the equation:

5x + 2y - 3x + y = S

Simplifying the left side:

2x + 3y = S

Therefore, the polynomial expression for the third side of the triangle is 2x + 3y.

To find the third side of the triangle, you can use the fact that the sum of the lengths of any two sides of a triangle must be greater than the length of the third side.

In this case, you are given two sides:
1. First side: 2x - 3y
2. Second side: x + 2y

To represent the third side, let's call it "z". According to the triangle inequality theorem, we have the following relationship:

(2x - 3y) + (x + 2y) > z

Simplifying this inequality, we get:

3x - y > z

Since P = 5x + 2y, we can substitute P into the inequality:

3x - y > P

Now, to express "z" (or the third side) as a polynomial expression, we rearrange the inequality by isolating "z":

z < 3x - y

Therefore, the polynomial expression representing the third side of the triangle is:

z = 3x - y