Answer:
a. 4x³+13x²+9
Explanation:
1. Distribute 4x to every term in the second set of parenthesis to get:
4x³-16x²+12x
2. Distribute 3 to every term in the second set of parenthesis to get:
3x²-12x+9
3. Add/subtract terms with the same variables/degrees:
4x³-16x²+12x+3x²-12x+9
4. The simplified answer is:
4x³+13x²+9