Left parenthesis, minus, x, cubed, minus, x, right parenthesis, plus, left parenthesis, 6, x, squared, plus, 6, x, minus, 7, right parenthesis, equals

(-x³ - x) + (6x² + 6x - 7)

= - x³ + 6x² + 5x - 7

Step-by-step explanation:

Given the function:

(-x³ - x) + (6x² + 6x - 7)

This can be simplified to

-x³ - x + 6x² + 6x - 7

Collecting like terms, we have

-x³ + 6x² - x + 6x - 7

= - x³ + 6x² + 5x - 7