(x²+x+1)+(x²-x+1)

To simplify the expression, let's combine like terms:

(x² + x + 1) + (x² - x + 1)

Combine the terms in each set of parentheses: (x² + x²) + (x - x) + (1 + 1)

Combine the like terms: 2x² + 0x + 2

Simplifying further, we can remove the term with coefficient zero: 2x² + 2

Therefore, the simplified form of the expression (x² + x + 1) + (x² - x + 1) is 2x² + 2.