Discontinuities Functions
1. **Determine discontinuities of** $f(x) = \frac{x^2 - 3x - 10}{x + 2}$.
- Factor numerator: $x^2 - 3x - 10 = (x - 5)(x + 2)$.
- Simplify: $f(x) = \frac{(x - 5)(x + 2)}{x + 2}$, for $x \neq -2$.
- Discontinuity at $x = -2$ because denominator is zero.
- Since $(x+2)$ cancels, this is a removable discontinuity (hole).
2. **Determine discontinuities of piecewise function**
$$f(x) = \begin{cases} x + 3 & x \geq 2 \\ x^2 + 1 & x < 2 \end{cases}$$
- Check continuity at $x=2$.
- Left limit: $\lim_{x \to 2^-} x^2 + 1 = 4 + 1 = 5$.
- Right limit: $\lim_{x \to 2^+} x + 3 = 2 + 3 = 5$.
- Function value: $f(2) = 2 + 3 = 5$.
- Limits and function value equal, so continuous at $x=2$.
- No discontinuities.
3. **Determine discontinuities of** $f(x) = \frac{x^4 - 1}{x^2 - 1}$.
- Factor numerator: $x^4 - 1 = (x^2 - 1)(x^2 + 1)$.
- Denominator: $x^2 - 1 = (x - 1)(x + 1)$.
- Simplify: $f(x) = \frac{(x^2 - 1)(x^2 + 1)}{x^2 - 1} = x^2 + 1$, for $x \neq \pm 1$.
- Discontinuities at $x = 1$ and $x = -1$ (denominator zero).
- Since $(x^2 - 1)$ cancels, these are removable discontinuities.
4. **Determine discontinuities of** $f(x) = \frac{x^3 + x^2 - 17x + 15}{x^2 + 2x - 15}$.
- Factor denominator: $x^2 + 2x - 15 = (x + 5)(x - 3)$.
- Find zeros of numerator by testing roots:
- $f(3) = 27 + 9 - 51 + 15 = 0$, so $(x - 3)$ is factor.
- Divide numerator by $(x - 3)$: quotient $x^2 + 4x - 5$.
- Factor quotient: $(x + 5)(x - 1)$.
- Numerator factors: $(x - 3)(x + 5)(x - 1)$.
- Simplify $f(x) = \frac{(x - 3)(x + 5)(x - 1)}{(x + 5)(x - 3)} = x - 1$, for $x \neq -5, 3$.
- Discontinuities at $x = -5$ and $x = 3$.
- Both are removable discontinuities (factors cancel).
5. **Determine discontinuities of polynomial** $f(x) = x^3 - 7x$.
- Polynomials are continuous everywhere.
- No discontinuities.
6. **Determine discontinuities of** $f(x) = \frac{x^2 - 4}{x^2 - 5x + 6}$.
- Factor numerator: $x^2 - 4 = (x - 2)(x + 2)$.
- Factor denominator: $x^2 - 5x + 6 = (x - 2)(x - 3)$.
- Simplify: $f(x) = \frac{(x - 2)(x + 2)}{(x - 2)(x - 3)} = \frac{x + 2}{x - 3}$, for $x \neq 2$.
- Discontinuities at $x = 2$ and $x = 3$.
- At $x=2$, removable discontinuity (factor cancels).
- At $x=3$, vertical asymptote (denominator zero, no cancellation).
7. **Determine discontinuities of** $f(x) = \frac{x^2 + 3x + 2}{x^2 + 4x + 3}$.
- Factor numerator: $(x + 1)(x + 2)$.
- Factor denominator: $(x + 1)(x + 3)$.
- Simplify: $f(x) = \frac{(x + 1)(x + 2)}{(x + 1)(x + 3)} = \frac{x + 2}{x + 3}$, for $x \neq -1$.
- Discontinuities at $x = -1$ and $x = -3$.
- At $x = -1$, removable discontinuity.
- At $x = -3$, vertical asymptote.
**Summary:**
- Discontinuities occur where denominator is zero.
- If factor cancels with numerator, discontinuity is removable (hole).
- If factor does not cancel, discontinuity is infinite (vertical asymptote).
Check graphs on graphing calculators to confirm these discontinuities visually.