(x²+x+1)+(x²-x+1)

To add the expressions (x^2 + x + 1) and (x^2 - x + 1), we simply combine like terms.

The terms x^2 and x^2 remain unchanged because they have the same variable and exponent.

For the terms with x, we add (+x) and (-x) to get 0x.

For the constant terms 1 and 1, we add them together to get 2.

Putting it all together, the sum of (x^2 + x + 1) and (x^2 - x + 1) is:

2x^2 + 0x + 2

Simplifying further, we can remove the 0x term:

2x^2 + 2