Final answer:
To simplify the expression, distribute the negatives and positives through the parentheses, combine like terms, and the result is -13x³ - x², which is choice A.
Step-by-step explanation:
To simplify the given expression -(5x² + x³) + 4(x² – 3x³), we first distribute the negative sign through the first set of parentheses and then distribute the positive 4 through the second set.
We get: -5x² - x³ + 4x² - 12x³.
Now, we combine like terms by adding the coefficients of terms with the same power of x:
Combine x² terms: (-5 + 4)x² = -x²
Combine x³ terms: (-1 - 12)x³ = -13x³
Putting it all together, the simplified expression is -13x³ - x², which matches choice A: -4x³ - x².