1. Problem: Determine if the function $$f(x) = \frac{x^2 - x - 2}{x + 1}$$ is continuous at $$x=2$$ and $$x=-1$$.
2. Formula and rules: A function is continuous at a point if the limit as $$x$$ approaches that point equals the function's value there.
3. Simplify $$f(x)$$:
$$x^2 - x - 2 = (x-2)(x+1)$$
So,
$$f(x) = \frac{(x-2)(x+1)}{x+1}$$
Cancel common factor:
$$f(x) = \frac{(x-2)\cancel{(x+1)}}{\cancel{x+1}} = x-2, \quad x \neq -1$$
4. Check continuity at $$x=2$$:
$$f(2) = 2 - 2 = 0$$
Since $$f(x) = x-2$$ for $$x \neq -1$$, limit as $$x \to 2$$ is:
$$\lim_{x \to 2} f(x) = 2 - 2 = 0$$
Function is defined and limit equals value, so continuous at $$x=2$$.
5. Check continuity at $$x=-1$$:
Function is undefined at $$x=-1$$ (denominator zero), so not continuous at $$x=-1$$.
6. Problem: Is $$g(x) = \begin{cases} x^2 + 3x, & x \leq 0 \\ x, & 0 < x \leq 2 \\ 3x^2, & x > 2 \end{cases}$$ continuous at $$x=0$$ and $$x=2$$?
7. Check continuity at $$x=0$$:
Left limit:
$$\lim_{x \to 0^-} g(x) = 0^2 + 3\cdot0 = 0$$
Right limit:
$$\lim_{x \to 0^+} g(x) = 0$$
Value:
$$g(0) = 0^2 + 3\cdot0 = 0$$
Continuous at $$x=0$$.
8. Check continuity at $$x=2$$:
Left limit:
$$\lim_{x \to 2^-} g(x) = 2$$
Right limit:
$$\lim_{x \to 2^+} g(x) = 3 \cdot 2^2 = 12$$
Value:
$$g(2) = 2$$
Limits not equal, so not continuous at $$x=2$$.
9. Problem: Find constants $$a$$ and $$b$$ so that $$h(x) = \begin{cases} ax + 5, & x \leq 1 \\ -2x^2 - 9, & -1 < x \leq 5 \\ 3x + b, & x > 5 \end{cases}$$ is continuous everywhere.
10. Continuity at $$x=1$$:
From left:
$$h(1) = a \cdot 1 + 5 = a + 5$$
From right:
$$h(1) = -2(1)^2 - 9 = -2 - 9 = -11$$
Set equal:
$$a + 5 = -11 \Rightarrow a = -16$$
11. Continuity at $$x=5$$:
From left:
$$h(5) = -2(5)^2 - 9 = -2 \cdot 25 - 9 = -50 - 9 = -59$$
From right:
$$h(5) = 3 \cdot 5 + b = 15 + b$$
Set equal:
$$15 + b = -59 \Rightarrow b = -74$$
12. Problem: Determine if $$f(x) = x^3 + x^2 - 2$$ is continuous at $$x=1$$.
13. Polynomial functions are continuous everywhere, so $$f(x)$$ is continuous at $$x=1$$.
14. Problem: Determine if $$f(x) = \frac{x^2 - x - 2}{x - 2}$$ is continuous at $$x=0$$.
15. Simplify numerator:
$$x^2 - x - 2 = (x-2)(x+1)$$
So,
$$f(x) = \frac{(x-2)(x+1)}{x-2}$$
Cancel common factor:
$$f(x) = \cancel{\frac{(x-2)}{(x-2)}} (x+1) = x+1, \quad x \neq 2$$
16. At $$x=0$$:
$$f(0) = 0 + 1 = 1$$
Limit as $$x \to 0$$:
$$\lim_{x \to 0} f(x) = 0 + 1 = 1$$
Function is continuous at $$x=0$$.
17. Problem: Find interval of length 1 containing a root of $$f(x) = x^3 - 3x + 5$$ using Intermediate Value Theorem (IVT).
18. Evaluate $$f(x)$$ at integer points:
$$f(-3) = (-3)^3 - 3(-3) + 5 = -27 + 9 + 5 = -13$$
$$f(-2) = (-2)^3 - 3(-2) + 5 = -8 + 6 + 5 = 3$$
19. Since $$f(-3) < 0$$ and $$f(-2) > 0$$, by IVT there is a root in $$(-3, -2)$$.
Final answers:
- $$f(x)$$ continuous at $$x=2$$ but not at $$x=-1$$.
- $$g(x)$$ continuous at $$x=0$$ but not at $$x=2$$.
- $$a = -16$$ and $$b = -74$$ for $$h(x)$$ continuous everywhere.
- $$f(x) = x^3 + x^2 - 2$$ continuous at $$x=1$$.
- $$f(x) = \frac{x^2 - x - 2}{x-2}$$ continuous at $$x=0$$.
- Root of $$f(x) = x^3 - 3x + 5$$ lies in interval $$(-3, -2)$$.
Continuity Problems Ecb67D
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