Answer:
The sum = 3x³ + x² - x + 3
Explanation:
It is given that,
 (x³ + 3x² + x + 1) + (2x³ - 2x² - 2x + 2)
To find the sum 
 (x³ + 3x² + x + 1) + (2x³ - 2x² - 2x + 2) 
 = x³ + 2x³ + 3x² - 2x² + x - 2x + 1 +2
 = 3x³ + x² - x + 3
Therefore the sum = 3x³ + x² - x + 3