Limits Expressions
1. **Problem statement:** Evaluate the following limits and analyze the given functions and expressions step-by-step.
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2. **Limit 1:** $$\lim_{x \to 1} \frac{\sqrt[3]{x} + 7 - 2}{x - 1}$$
- Substitute $x=1$: numerator $= \sqrt[3]{1} + 7 - 2 = 1 + 7 - 2 = 6$
- Denominator $= 1 - 1 = 0$
- This is a form $\frac{6}{0}$ which tends to infinity or does not exist.
- Check left and right limits:
- As $x \to 1^-$, denominator $<0$, fraction tends to $-\infty$
- As $x \to 1^+$, denominator $>0$, fraction tends to $+\infty$
- **Conclusion:** Limit does not exist.
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3. **Limit 2:** $$\lim_{x \to +\infty} \frac{x - \sqrt[3]{x^2}}{x}$$
- Rewrite numerator: $x - x^{2/3}$
- Divide numerator and denominator by $x$:
$$\frac{x - x^{2/3}}{x} = 1 - x^{-1/3}$$
- As $x \to +\infty$, $x^{-1/3} \to 0$
- So limit $= 1 - 0 = 1$
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4. **Limit 3:** $$\lim_{x \to -\infty} \sqrt[3]{x^3} - x + 3x$$
- Note $\sqrt[3]{x^3} = x$
- Expression simplifies to $x - x + 3x = 3x$
- As $x \to -\infty$, $3x \to -\infty$
- **Limit:** $-\infty$
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5. **Limit 4:** Same as Limit 2, so answer is $1$.
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6. **Expression A:** $$A = \frac{\sqrt[4]{9} \cdot \sqrt[3]{3} \cdot \sqrt[3]{9}}{\sqrt[5]{81} \cdot x \cdot \sqrt{\sqrt{3}}}$$
- Simplify numerator:
- $\sqrt[4]{9} = 9^{1/4} = (3^2)^{1/4} = 3^{1/2} = \sqrt{3}$
- $\sqrt[3]{3} = 3^{1/3}$
- $\sqrt[3]{9} = 9^{1/3} = (3^2)^{1/3} = 3^{2/3}$
- Numerator combined: $\sqrt{3} \cdot 3^{1/3} \cdot 3^{2/3} = 3^{1/2} \cdot 3^{1/3 + 2/3} = 3^{1/2 + 1} = 3^{3/2}$
- Denominator:
- $\sqrt[5]{81} = 81^{1/5} = (3^4)^{1/5} = 3^{4/5}$
- $\sqrt{\sqrt{3}} = (3^{1/2})^{1/2} = 3^{1/4}$
- Denominator combined: $3^{4/5} \cdot x \cdot 3^{1/4} = x \cdot 3^{4/5 + 1/4} = x \cdot 3^{(16/20 + 5/20)} = x \cdot 3^{21/20}$
- So,
$$A = \frac{3^{3/2}}{x \cdot 3^{21/20}} = \frac{3^{30/20}}{x \cdot 3^{21/20}} = \frac{3^{9/20}}{x}$$
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7. **Expression B:** $$B = \frac{\sqrt[15]{35} \cdot \sqrt[3]{9} \cdot \sqrt[5]{93}}{\sqrt[5]{3}}$$
- Simplify each term:
- $\sqrt[15]{35} = 35^{1/15}$
- $\sqrt[3]{9} = 9^{1/3} = (3^2)^{1/3} = 3^{2/3}$
- $\sqrt[5]{93} = 93^{1/5}$
- $\sqrt[5]{3} = 3^{1/5}$
- Combine numerator powers of 3:
- $3^{2/3} \cdot 93^{1/5} \cdot 35^{1/15}$ (cannot simplify 35 and 93 further)
- Divide by $3^{1/5}$:
$$B = 35^{1/15} \cdot 93^{1/5} \cdot 3^{2/3 - 1/5} = 35^{1/15} \cdot 93^{1/5} \cdot 3^{(10/15 - 3/15)} = 35^{1/15} \cdot 93^{1/5} \cdot 3^{7/15}$$
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8. **Function:** $$f(x) = \frac{x^2}{x - 1}$$
- Domain: $x \neq 1$
- Derivative given:
$$f'(x) = \frac{x^2 - 2x}{(x - 1)^2}$$
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9. **Inverse function values:**
- Given $g^{-1}(4 \sqrt[3]{5})$, $g^{-1}(4 \sqrt{2})$, $g^{-1}(4 \sqrt[6]{10})$
- Without explicit $g$, cannot find exact values.
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10. **Equation (E):** $$x^3 = 3x - 3$$
- Has one unique real root $\alpha$.
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11. **Function at root:**
- $$f(\alpha) = \frac{3}{\alpha}$$
- Given inequality:
$$-\frac{3}{2} < f(\alpha) < -1$$
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12. **Function:** $$f(x) = \sqrt[3]{x} + 1$$
- Inverse function $f^{-1}(y)$ satisfies:
$$y = \sqrt[3]{x} + 1 \implies \sqrt[3]{x} = y - 1 \implies x = (y - 1)^3$$
- So,
$$f^{-1}(y) = (y - 1)^3$$
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**Final answers:**
- Limit 1: Does not exist
- Limit 2: $1$
- Limit 3: $-\infty$
- Limit 4: $1$
- Expression A: $\frac{3^{9/20}}{x}$
- Expression B: $35^{1/15} \cdot 93^{1/5} \cdot 3^{7/15}$
- $f'(x) = \frac{x^2 - 2x}{(x - 1)^2}$
- $f^{-1}(y) = (y - 1)^3$