(x²+x+1)+(x²-x+1)

To add these two expressions, we can simply combine like terms.

(x² + x + 1) + (x² - x + 1)

First, let's combine the x² terms: x² + x² = 2x²

Next, let's combine the x terms: x - x = 0

Lastly, let's combine the constant terms: 1 + 1 = 2

Putting it all together, the simplified expression is: 2x² + 2