3. (2*x*^{2} - 3*x* + 5) + (*x*^{2} + 4*x* - 6)

This is an addition of polynomials problem. Therules for adding polynomials is "Remove parentheses and combine like terms."

Remove parentheses

2*x*^{2} - 3*x* + 5 + *x*^{2} + 4*x* - 6

If there is nothing in front of the parentheses except maybe a plus sign, then nothing happens when you remove them. Now combine like terms.

2*x*^{2} + *x*^{2} - 3*x* + 4*x* + 5 - 6

3*x*^{2} + *x* - 1