You can eliminate parentheses and combine like terms.
(2x^2 +4x-9) +(3x^2-2x+10)
= 2x^2 +4x-9 +3x^2-2x+10 . . . . . nothing needs to be distributed, so we can simply drop the parentheses
= x^2(2 +3) +x(4 -2) +(-9 +10) . . . group like terms
= 5x^2 +2x +1