Limit Polynomial
1. **State the problem:** We need to find the limit
$$\lim_{x \to -1} \frac{x^3 + 3x^2 + x - 1}{x + 1}$$
2. **Check direct substitution:** Substitute $x = -1$ into numerator and denominator:
Numerator: $(-1)^3 + 3(-1)^2 + (-1) - 1 = -1 + 3 - 1 - 1 = 0$
Denominator: $-1 + 1 = 0$
Since direct substitution gives $\frac{0}{0}$, an indeterminate form, we need to simplify.
3. **Factor the numerator:** Use polynomial division or factor by synthetic division to divide $x^3 + 3x^2 + x - 1$ by $x + 1$.
Divide:
$$x^3 + 3x^2 + x - 1 \div (x + 1)$$
- First term: $x^2$ because $x^2 \times (x + 1) = x^3 + x^2$
- Subtract: $(x^3 + 3x^2) - (x^3 + x^2) = 2x^2$
- Bring down $+ x$: now $2x^2 + x$
- Next term: $+ 2x$ because $2x \times (x + 1) = 2x^2 + 2x$
- Subtract: $(2x^2 + x) - (2x^2 + 2x) = -x$
- Bring down $-1$: now $-x - 1$
- Next term: $-1$ because $-1 \times (x + 1) = -x - 1$
- Subtract: $(-x - 1) - (-x - 1) = 0$
So,
$$x^3 + 3x^2 + x - 1 = (x + 1)(x^2 + 2x - 1)$$
4. **Simplify the limit expression:**
$$\frac{x^3 + 3x^2 + x - 1}{x + 1} = \frac{(x + 1)(x^2 + 2x - 1)}{x + 1} = x^2 + 2x - 1, \quad x \neq -1$$
5. **Evaluate the limit:** Now substitute $x = -1$ into the simplified expression:
$$(-1)^2 + 2(-1) - 1 = 1 - 2 - 1 = -2$$
**Final answer:**
$$\lim_{x \to -1} \frac{x^3 + 3x^2 + x - 1}{x + 1} = -2$$