Final answer:
To simplify the given expression, distribute the subtraction sign, combine like terms, and simplify to get -2n³ - 5n² + 8 as the correct answer.
Step-by-step explanation:
The question requires simplifying the expression (-9n⁴ + 8) - (-9n⁴ + 2n³ + 5n²). To simplify, you distribute the subtraction sign across the terms in the second set of parentheses, which will change the signs of the terms inside those parentheses. This yields the following steps:
- Remove parentheses: -9n⁴ + 8 + 9n⁴ - 2n³ - 5n²
- Combine like terms: -9n⁴ cancels with +9n⁴, and you're left with -2n³ - 5n² + 8.
Thus, the correct answer is (b) -2n³ - 5n² + 8.