Find the equation of the tangent to the curve $y = \frac{\sqrt{x}-2}{\sqrt[3]{x}}$ at P (1, -1).
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Understand the Problem
The question asks to find the equation of the tangent line to the given curve at the specified point. This requires finding the derivative of the function, evaluating it at the given x-coordinate to find the slope, and then using the point-slope form to determine the equation of the tangent line.
Answer
$y = \frac{5}{6}x - \frac{11}{6}$
Answer for screen readers
$y = \frac{5}{6}x - \frac{11}{6}$
Steps to Solve
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Rewrite the function in terms of exponents Rewrite the function $y = \frac{\sqrt{x}-2}{\sqrt[3]{x}}$ using exponents instead of radicals: $y = \frac{x^{1/2}-2}{x^{1/3}}$
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Apply the quotient rule Differentiate $y$ with respect to $x$ using the quotient rule: $\frac{d}{dx}(\frac{u}{v}) = \frac{v\frac{du}{dx} - u\frac{dv}{dx}}{v^2}$. Here, $u = x^{1/2} - 2$ and $v = x^{1/3}$.
$\frac{du}{dx} = \frac{1}{2}x^{-1/2}$ $\frac{dv}{dx} = \frac{1}{3}x^{-2/3}$
Now, apply the quotient rule: $\frac{dy}{dx} = \frac{x^{1/3}(\frac{1}{2}x^{-1/2}) - (x^{1/2}-2)(\frac{1}{3}x^{-2/3})}{(x^{1/3})^2}$ $\frac{dy}{dx} = \frac{\frac{1}{2}x^{-1/6} - \frac{1}{3}x^{-1/6} + \frac{2}{3}x^{-2/3}}{x^{2/3}}$
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Simplify the derivative Simplify the expression: $\frac{dy}{dx} = \frac{\frac{1}{6}x^{-1/6} + \frac{2}{3}x^{-2/3}}{x^{2/3}}$ $\frac{dy}{dx} = \frac{1}{6}x^{-1/6 - 2/3} + \frac{2}{3}x^{-2/3 - 2/3}$ $\frac{dy}{dx} = \frac{1}{6}x^{-5/6} + \frac{2}{3}x^{-4/3}$
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Evaluate the derivative at $x=1$ Substitute $x=1$ into the derivative to find the slope of the tangent at the point $(1, -1)$: $m = \frac{dy}{dx}\Big|_{x=1} = \frac{1}{6}(1)^{-5/6} + \frac{2}{3}(1)^{-4/3} = \frac{1}{6} + \frac{2}{3} = \frac{1}{6} + \frac{4}{6} = \frac{5}{6}$
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Find the equation of the tangent line Use the point-slope form of a line: $y - y_1 = m(x - x_1)$, where $(x_1, y_1) = (1, -1)$ and $m = \frac{5}{6}$. $y - (-1) = \frac{5}{6}(x - 1)$ $y + 1 = \frac{5}{6}x - \frac{5}{6}$ $y = \frac{5}{6}x - \frac{5}{6} - 1$ $y = \frac{5}{6}x - \frac{5}{6} - \frac{6}{6}$ $y = \frac{5}{6}x - \frac{11}{6}$
$y = \frac{5}{6}x - \frac{11}{6}$
More Information
The equation of the tangent line to the curve $y = \frac{\sqrt{x}-2}{\sqrt[3]{x}}$ at the point $(1, -1)$ is $y = \frac{5}{6}x - \frac{11}{6}$. This line touches the curve at the specified point and has the same slope as the curve at that point.
Tips
A common mistake is to incorrectly apply the quotient rule or to make errors when simplifying the derivative. Another common mistake is with handling fractional exponents. Additionally, mistakes may arise when solving for the final equation of the tangent line. Carefully checking each step of the process helps in avoiding these errors.
Another common mistake is failing to correctly simplify $x^{-1/6-2/3}$ and $x^{-2/3-2/3}$. Remember to convert to common denominators when subtracting fractions.
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