Sunday, May 27, 2018

Calculus and Its Applications, Chapter 1, 1.5, Section 1.5, Problem 48

If $\displaystyle y = x^{-\frac{3}{4}} - 3x^{\frac{2}{3}} + x^{\frac{5}{4}} + \frac{2}{x^4}$, find $y'$

$
\begin{equation}
\begin{aligned}
y' &= \frac{d}{dx} \left( x^{-\frac{3}{4}} - 3x^{\frac{2}{3}} + x^{\frac{5}{4}} + \frac{2}{x^4} \right)\\
\\
&= \frac{d}{dx} \left( x^{-\frac{3}{4}} \right) - \frac{d}{dx} \left( 3x^{\frac{2}{3}}\right) + \frac{d}{dx} \left( x^{\frac{5}{4}} \right)+ \frac{d}{dx} \left( \frac{2}{x^4} \right)\\
\\
&= \frac{d}{dx} \left( x^{-\frac{3}{4}} \right) - 3 \cdot \frac{d}{dx} \left( x^{\frac{2}{3}} \right) + \frac{d}{dx} \left( x^{\frac{5}{4}} \right) +
2 \cdot \frac{d}{dx} \left( x^{-4} \right)\\
\\
&= -\frac{3}{4} \cdot x^{-\frac{3}{4}-1} - 3 \cdot \frac{2}{3} x^{\frac{2}{3} - 1} + \frac{5}{4} \cdot x^{\frac{5}{4}-1} + 2 \cdot (-4) x^{-4-1}\\
\\
&= -\frac{3}{4}x^{-\frac{7}{4}} - 2 x^{-\frac{1}{3}} + \frac{5}{4} x^{\frac{1}{4}} - 8x^{-5}\\
\\
&= \frac{-3}{4x^{\frac{7}{4}}} - \frac{2}{x^{\frac{1}{3}}} + \frac{5}{4} x^{\frac{1}{4}} - \frac{8}{x^5}

\end{aligned}
\end{equation}
$

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