Limits Graph Functions
1. **Problem 1: Limits from the graph of function $f(x)$**
(a) Find $\lim_{x \to 1} f(x)$.
- From the graph, as $x$ approaches 1 from both sides, $f(x)$ approaches just above 1.
- The open circle at $(1,1)$ means $f(1)=1$ but the limit depends on nearby values.
- The function values near 1 approach approximately 1 from the left and right.
- So, $\lim_{x \to 1} f(x) = 1$.
(b) Find $\lim_{x \to 2} f(x)$.
- As $x$ approaches 2, the function approaches 2 from the left (open circle at (2,2)) and 1.5 from the right (filled dot at (2,1.5)).
- Since left and right limits differ, the limit does not exist.
- So, $\lim_{x \to 2} f(x)$ does not exist.
(c) Find $\lim_{x \to 3} f(x)$.
- Left limit at 3 is near 2 (open circle at (3,2)), right limit is 1 (filled dot at (3,1)).
- Left and right limits differ, so limit does not exist.
(d) Find $\lim_{x \to 4} f(x)$.
- The function steps up to 1.5 at $x=4$ and rises smoothly after.
- Both sides approach 1.5.
- So, $\lim_{x \to 4} f(x) = 1.5$.
(e) Find $\lim_{x \to +\infty} f(x)$.
- The function approaches horizontal asymptote $y=3$ as $x \to +\infty$.
- So, $\lim_{x \to +\infty} f(x) = 3$.
(f) Find $\lim_{x \to -\infty} f(x)$.
- The function starts near 0 at $x=-1$ and increases gradually.
- No explicit asymptote given, assume $\lim_{x \to -\infty} f(x) = 0$.
(g) Find $\lim_{x \to 3^+} f(x)$.
- Right-hand limit at 3 is the filled dot at 1.
- So, $\lim_{x \to 3^+} f(x) = 1$.
(h) Find $\lim_{x \to 3^-} f(x)$.
- Left-hand limit at 3 is near 2 (open circle).
- So, $\lim_{x \to 3^-} f(x) = 2$.
(i) Find $\lim_{x \to 0} f(x)$.
- From graph, near $x=0$, $f(x)$ is near 0.
- So, $\lim_{x \to 0} f(x) = 0$.
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2. **Problem 2: Limits of given functions**
(a) $f(x) = \sqrt{5 - x}$
- Find $\lim_{x \to 0} \sqrt{5 - x} = \sqrt{5 - 0} = \sqrt{5}$.
- Find $\lim_{x \to 5^+} \sqrt{5 - x}$.
- For $x > 5$, $5 - x < 0$, square root not real, so limit does not exist in reals.
- Find $\lim_{x \to -5^-} \sqrt{5 - x}$.
- At $x \to -5^-$, $5 - (-5) = 10$, so $\sqrt{10}$.
- Find $\lim_{x \to -5} \sqrt{5 - x} = \sqrt{10}$.
- Find $\lim_{x \to 5} \sqrt{5 - x}$ from left side only (since right side not real).
- $\lim_{x \to 5^-} \sqrt{5 - x} = 0$.
- Find $\lim_{x \to -\infty} \sqrt{5 - x}$.
- As $x \to -\infty$, $5 - x \to +\infty$, so limit is $+\infty$.
- Find $\lim_{x \to +\infty} \sqrt{5 - x}$.
- For large $x$, $5 - x$ negative, no real values, limit does not exist.
(b)
$$f(x) = \begin{cases} \frac{x-5}{|x-5|}, & x \neq 5 \\ 0, & x=5 \end{cases}$$
- Find $\lim_{x \to 0} f(x)$.
- For $x$ near 0, $x \neq 5$, so $f(x) = \frac{x-5}{|x-5|}$.
- At $x=0$, $0-5 = -5$, $|0-5|=5$, so $f(0) = -1$.
- Limit as $x \to 0$ is $-1$.
- Find $\lim_{x \to 5^+} f(x)$.
- For $x > 5$, $x-5 > 0$, so $f(x) = \frac{x-5}{x-5} = 1$.
- Find $\lim_{x \to -5^-} f(x)$.
- For $x < -5$, $x-5 < 0$, so $f(x) = -1$.
- Find $\lim_{x \to -5} f(x)$.
- Left and right limits at $-5$ are both $-1$, so limit is $-1$.
- Find $\lim_{x \to 5} f(x)$.
- Left limit at 5: $x < 5$, $f(x) = -1$.
- Right limit at 5: $x > 5$, $f(x) = 1$.
- Limits differ, so limit does not exist.
- Find $\lim_{x \to -\infty} f(x)$.
- For very large negative $x$, $x-5 < 0$, so $f(x) = -1$.
- Find $\lim_{x \to +\infty} f(x)$.
- For very large positive $x$, $x-5 > 0$, so $f(x) = 1$.
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**Final answers:**
1. (a) 1
(b) Does not exist
(c) Does not exist
(d) 1.5
(e) 3
(f) 0
(g) 1
(h) 2
(i) 0
2. (a)
$\lim_{x \to 0} = \sqrt{5}$
$\lim_{x \to 5^+}$ does not exist (not real)
$\lim_{x \to -5^-} = \sqrt{10}$
$\lim_{x \to -5} = \sqrt{10}$
$\lim_{x \to 5^-} = 0$
$\lim_{x \to -\infty} = +\infty$
$\lim_{x \to +\infty}$ does not exist (not real)
(b)
$\lim_{x \to 0} = -1$
$\lim_{x \to 5^+} = 1$
$\lim_{x \to -5^-} = -1$
$\lim_{x \to -5} = -1$
$\lim_{x \to 5}$ does not exist
$\lim_{x \to -\infty} = -1$
$\lim_{x \to +\infty} = 1$