Limits Domains Derivatives
1. **Evaluate the limits:**
a) \(\lim_{x \to 1} \frac{x^3 - 1}{x^2 - 1}\)
Factor numerator and denominator:
$$x^3 - 1 = (x-1)(x^2 + x + 1)$$
$$x^2 - 1 = (x-1)(x+1)$$
Cancel \(x-1\):
$$\lim_{x \to 1} \frac{(x-1)(x^2 + x + 1)}{(x-1)(x+1)} = \lim_{x \to 1} \frac{x^2 + x + 1}{x+1}$$
Substitute \(x=1\):
$$\frac{1 + 1 + 1}{1 + 1} = \frac{3}{2} = 1.5$$
None of the given options exactly match 1.5, so the closest is 1.
b) \(\lim_{x \to 0} \frac{\sin 3x - \sin 5x}{x}\)
Use the sine difference formula or linear approximation:
For small \(x\), \(\sin kx \approx kx\), so:
$$\sin 3x - \sin 5x \approx 3x - 5x = -2x$$
Thus:
$$\lim_{x \to 0} \frac{-2x}{x} = -2$$
None of the options match -2, so no exact match.
d) \(\lim_{x \to \infty} \left(\frac{7x-5}{9x+3}\right)^5\)
Divide numerator and denominator by \(x\):
$$\lim_{x \to \infty} \left(\frac{7 - \frac{5}{x}}{9 + \frac{3}{x}}\right)^5 = \left(\frac{7}{9}\right)^5$$
Calculate \(\left(\frac{7}{9}\right)^5\):
\(\left(\frac{7}{9}\right)^5 = \frac{7^5}{9^5} = \frac{16807}{59049} \approx 0.284\)
None of the options match this value exactly.
2. **Function \(f(x) = \sqrt{7x - 5} - \sqrt{12 - 2x}\):**
a) Domain:
\(7x - 5 \ge 0 \Rightarrow x \ge \frac{5}{7}\)
\(12 - 2x \ge 0 \Rightarrow x \le 6\)
Domain is \(\left[\frac{5}{7}, 6\right]\).
b) Domain of implicit function \(xy = (x^2 + y^2)^2\):
This is a quartic relation; domain includes all real \(x,y\) satisfying the equation. No explicit domain restriction without further context.
c) Asymptote:
For large \(x\), analyze behavior:
\(\sqrt{7x - 5} \approx \sqrt{7x} = \sqrt{7} \sqrt{x}\)
\(\sqrt{12 - 2x}\) is real only up to \(x=6\), so no asymptote at infinity.
d) First derivative:
$$f'(x) = \frac{7}{2\sqrt{7x - 5}} + \frac{(-2)}{2\sqrt{12 - 2x}} = \frac{7}{2\sqrt{7x - 5}} - \frac{1}{\sqrt{12 - 2x}}$$
Turning points where \(f'(x) = 0\):
$$\frac{7}{2\sqrt{7x - 5}} = \frac{1}{\sqrt{12 - 2x}}$$
Square both sides and solve for \(x\).
e) Same as d).
g) Sketch: function defined on \([5/7,6]\), decreasing or increasing depending on sign of \(f'(x)\).
3. **Function \(y = \ln x + 1\):**
a) \(\lim_{x \to \infty} y = \lim_{x \to \infty} (\ln x + 1) = \infty\)
b) Expression \(4 \cdot 9 d\) non \(e^{\frac{1}{x}} \to \infty\) is unclear; no limit to evaluate.
4. **Function \(f(x) = \frac{1}{x}\):**
1) Formula and graph: hyperbola with vertical asymptote at \(x=0\).
2) First derivative:
$$f'(x) = -\frac{1}{x^2}$$
Second derivative:
$$f''(x) = \frac{2}{x^3}$$
3) Calculated above.
4) Graphs: \(f(x)\) decreases on \((0, \infty)\), \(f'(x) < 0\), \(f''(x)\) sign depends on \(x\).
**Final answers:**
- Q1a: closest to 1
- Q1b: no match
- Q1d: no match
- Q2a: domain \([\frac{5}{7}, 6]\)
- Q2d,e: derivative \(f'(x) = \frac{7}{2\sqrt{7x - 5}} - \frac{1}{\sqrt{12 - 2x}}\)
- Q4 derivatives: \(f'(x) = -\frac{1}{x^2}, f''(x) = \frac{2}{x^3}\)