Subtract: (6x² + 3x + 4) - (-5x³ + 2x² - 9)

What would be the next step in solving this problem?

a. (6x² + 5x³) + (3x + 2x²) + (4 - 9)

b. (6x² + 2x²) + (3x - 5x³) + (4 + 9)

c. (6x² + 2x²) + (4-9) + 3x - 5x³

d. (6x² + 3x + 4) + (5x³ - 2x² + 9)

d. (6x² + 3x + 4) + (5x³ - 2x² - 9)

Step-by-step explanation:

An appropriate next step is to distribute the effect of the minus sign on the second set of parentheses. This will let you eliminate parentheses.

a. inappropriate grouping, and the signs of 2x² and 9 are incorrect

b. inappropriate grouping, and the signs of 2x² and 5x³ are incorrect

c. the signs of 2x², 9, and 5x³ are incorrect

d. the appropriate choice