1. **State the problem:**
We are given two polynomials:
$$P(x) = -3x^3 + 2x^2 - 1$$
$$Q(x) = 5 + x + 2x^4$$
We need to find the derivatives of the product $(P \times Q)(x)$ and the sum $(P + Q)(x)$.
2. **Recall the formulas:**
- Derivative of a product: $\frac{d}{dx}[P(x)Q(x)] = P'(x)Q(x) + P(x)Q'(x)$
- Derivative of a sum: $\frac{d}{dx}[P(x) + Q(x)] = P'(x) + Q'(x)$
3. **Find the derivatives of $P(x)$ and $Q(x)$:**
$$P'(x) = \frac{d}{dx}(-3x^3 + 2x^2 - 1) = -9x^2 + 4x$$
$$Q'(x) = \frac{d}{dx}(5 + x + 2x^4) = 0 + 1 + 8x^3 = 1 + 8x^3$$
4. **Compute the derivative of the product:**
$$\frac{d}{dx}[P(x)Q(x)] = P'(x)Q(x) + P(x)Q'(x)$$
Substitute:
$$= (-9x^2 + 4x)(5 + x + 2x^4) + (-3x^3 + 2x^2 - 1)(1 + 8x^3)$$
5. **Expand each term:**
First term:
$$(-9x^2)(5) = -45x^2$$
$$(-9x^2)(x) = -9x^3$$
$$(-9x^2)(2x^4) = -18x^6$$
$$(4x)(5) = 20x$$
$$(4x)(x) = 4x^2$$
$$(4x)(2x^4) = 8x^5$$
Sum first term:
$$-45x^2 - 9x^3 - 18x^6 + 20x + 4x^2 + 8x^5$$
Simplify:
$$-18x^6 + 8x^5 - 9x^3 + (-45x^2 + 4x^2) + 20x = -18x^6 + 8x^5 - 9x^3 - 41x^2 + 20x$$
Second term:
$$(-3x^3)(1) = -3x^3$$
$$(-3x^3)(8x^3) = -24x^6$$
$$(2x^2)(1) = 2x^2$$
$$(2x^2)(8x^3) = 16x^5$$
$$(-1)(1) = -1$$
$$(-1)(8x^3) = -8x^3$$
Sum second term:
$$-3x^3 - 24x^6 + 2x^2 + 16x^5 - 1 - 8x^3$$
Simplify:
$$-24x^6 + 16x^5 + (-3x^3 - 8x^3) + 2x^2 - 1 = -24x^6 + 16x^5 - 11x^3 + 2x^2 - 1$$
6. **Add both terms:**
$$(-18x^6 + 8x^5 - 9x^3 - 41x^2 + 20x) + (-24x^6 + 16x^5 - 11x^3 + 2x^2 - 1)$$
Combine like terms:
$$(-18x^6 - 24x^6) + (8x^5 + 16x^5) + (-9x^3 - 11x^3) + (-41x^2 + 2x^2) + 20x - 1$$
$$= -42x^6 + 24x^5 - 20x^3 - 39x^2 + 20x - 1$$
7. **Compute the derivative of the sum:**
$$\frac{d}{dx}[P(x) + Q(x)] = P'(x) + Q'(x) = (-9x^2 + 4x) + (1 + 8x^3)$$
Simplify:
$$8x^3 - 9x^2 + 4x + 1$$
**Final answers:**
- $$\frac{d}{dx}[P(x)Q(x)] = -42x^6 + 24x^5 - 20x^3 - 39x^2 + 20x - 1$$
- $$\frac{d}{dx}[P(x) + Q(x)] = 8x^3 - 9x^2 + 4x + 1$$
Derivatives Product Sum 2Ec212
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