1. **Stating the problem:**
We have two polynomials:
$$P = 4x^3 + 3x^2 - x + 3$$
$$Q = x^3 - x + 1$$
We need to find:
a) The degree of $P+Q$.
b) The degree of $PQ$.
c) The coefficient of the $x^3$ term in $PQ$.
2. **Find the degree of $P+Q$:**
Add $P$ and $Q$ term by term:
$$P+Q = (4x^3 + 3x^2 - x + 3) + (x^3 - x + 1)$$
Combine like terms:
$$= (4x^3 + x^3) + 3x^2 + (-x - x) + (3 + 1)$$
$$= 5x^3 + 3x^2 - 2x + 4$$
The highest power of $x$ with a nonzero coefficient is $3$, so the degree of $P+Q$ is $3$.
3. **Find the degree of $PQ$:**
The degree of a product of polynomials is the sum of their degrees.
Degree of $P$ is $3$ (highest power in $4x^3$).
Degree of $Q$ is $3$ (highest power in $x^3$).
Therefore,
$$\text{degree}(PQ) = 3 + 3 = 6$$
4. **Find the coefficient of the $x^3$ term in $PQ$:**
Write $P$ and $Q$ explicitly:
$$P = 4x^3 + 3x^2 - x + 3$$
$$Q = x^3 + 0x^2 - x + 1$$
To find the coefficient of $x^3$ in $PQ$, consider all pairs of terms from $P$ and $Q$ whose powers add to $3$:
- $4x^3$ from $P$ and constant term $1$ from $Q$: power sum $3 + 0 = 3$, product $4 \times 1 = 4$
- $3x^2$ from $P$ and $-x$ from $Q$: power sum $2 + 1 = 3$, product $3 \times (-1) = -3$
- $-x$ from $P$ and $0x^2$ from $Q$: power sum $1 + 2 = 3$, product $-1 \times 0 = 0$
- $3$ from $P$ and $x^3$ from $Q$: power sum $0 + 3 = 3$, product $3 \times 1 = 3$
Sum these contributions:
$$4 + (-3) + 0 + 3 = 4$$
**Final answers:**
a) Degree of $P+Q$ is $3$.
b) Degree of $PQ$ is $6$.
c) Coefficient of $x^3$ in $PQ$ is $4$.
Polynomial Degrees
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