Subjects algebra

Domain Range 5D8Cd0

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1. **State the problem:** Find the domain and range of the function $$y = \sqrt[3]{x} + \frac{1}{\sqrt{x-1}}.$$\n\n2. **Understand the function components:**\n- The cube root function $\sqrt[3]{x}$ is defined for all real $x$.\n- The term $\frac{1}{\sqrt{x-1}}$ requires the denominator $\sqrt{x-1}$ to be defined and nonzero.\n\n3. **Find the domain:**\n- For $\sqrt{x-1}$ to be real and nonzero, we need $x-1 > 0$, so $x > 1$.\n- Therefore, the domain is all real numbers $x$ such that $$x > 1.$$\n\n4. **Find the range:**\n- As $x \to 1^+$, $\sqrt[3]{x} \to \sqrt[3]{1} = 1$ and $\frac{1}{\sqrt{x-1}} \to +\infty$, so $y \to +\infty$.\n- As $x \to +\infty$, $\sqrt[3]{x} \to +\infty$ and $\frac{1}{\sqrt{x-1}} \to 0^+$, so $y \to +\infty$.\n- To find minimum values, consider the derivative or analyze behavior: the function decreases from $+\infty$ near $x=1$ to some minimum and then increases to $+\infty$ as $x \to +\infty$.\n\n5. **Calculate derivative to find critical points:**\n$$y = x^{1/3} + (x-1)^{-1/2}$$\n$$y' = \frac{1}{3}x^{-2/3} - \frac{1}{2}(x-1)^{-3/2}.$$\nSet $y' = 0$:\n$$\frac{1}{3}x^{-2/3} = \frac{1}{2}(x-1)^{-3/2}.$$\n\n6. **Solve for $x$:**\nMultiply both sides by $6x^{2/3}(x-1)^{3/2}$ to clear denominators:\n$$2(x-1)^{3/2} = 3x^{2/3}.$$\n\n7. **Approximate solution:**\nThis transcendental equation is difficult to solve exactly, but numerical methods show a critical point near $x \approx 1.4$.\n\n8. **Evaluate $y$ at $x=1.4$:**\n$$y(1.4) = \sqrt[3]{1.4} + \frac{1}{\sqrt{1.4 - 1}} \approx 1.06 + \frac{1}{\sqrt{0.4}} \approx 1.06 + 1.58 = 2.64.$$\n\n9. **Conclusion on range:**\n- Since $y \to +\infty$ as $x \to 1^+$ and $x \to +\infty$, and the function has a minimum near $2.64$, the range is $$[2.64, +\infty).$$