Polynomial Multiplication
1. **State the problem:**
Multiply the two polynomials $$(x^2 + 5x + 4)(x^2 + 2x - 1)$$.
2. **Use the distributive property:**
Multiply each term in the first polynomial by each term in the second polynomial.
3. Multiply $x^2$ by each term:
$$x^2 \times x^2 = x^4$$
$$x^2 \times 2x = 2x^3$$
$$x^2 \times (-1) = -x^2$$
4. Multiply $5x$ by each term:
$$5x \times x^2 = 5x^3$$
$$5x \times 2x = 10x^2$$
$$5x \times (-1) = -5x$$
5. Multiply $4$ by each term:
$$4 \times x^2 = 4x^2$$
$$4 \times 2x = 8x$$
$$4 \times (-1) = -4$$
6. **Combine all terms:**
$$x^4 + 2x^3 - x^2 + 5x^3 + 10x^2 - 5x + 4x^2 + 8x - 4$$
7. **Group like terms:**
- $x^4$ term: $$x^4$$
- $x^3$ terms: $$2x^3 + 5x^3 = 7x^3$$
- $x^2$ terms: $$-x^2 + 10x^2 + 4x^2 = 13x^2$$
- $x$ terms: $$-5x + 8x = 3x$$
- Constant term: $$-4$$
8. **Final expanded polynomial:**
$$x^4 + 7x^3 + 13x^2 + 3x - 4$$