Question

assignment 4: problem 4 (1 point)
let $f(x)=-4x^{5}sqrt{x}+\frac{-7}{x^{2}sqrt{x}}$
$f(x)=square$
note: your answer should be a function of the variable x and not a number!

Explanation:

Step1: Rewrite the function

Rewrite $f(x)=-4x^{5}\sqrt{x}+\frac{-7}{x^{2}\sqrt{x}}$ as $f(x)=-4x^{5}x^{\frac{1}{2}}- 7x^{-2}x^{-\frac{1}{2}}=-4x^{\frac{10 + 1}{2}}-7x^{\frac{-4-1}{2}}=-4x^{\frac{11}{2}}-7x^{-\frac{5}{2}}$.

Step2: Apply the power - rule for differentiation

The power - rule states that if $y = x^{n}$, then $y^\prime=nx^{n - 1}$.
For $y=-4x^{\frac{11}{2}}$, $y^\prime=-4\times\frac{11}{2}x^{\frac{11}{2}-1}=-22x^{\frac{9}{2}}$.
For $y = - 7x^{-\frac{5}{2}}$, $y^\prime=-7\times(-\frac{5}{2})x^{-\frac{5}{2}-1}=\frac{35}{2}x^{-\frac{7}{2}}$.

Step3: Combine the derivatives

$f^\prime(x)=-22x^{\frac{9}{2}}+\frac{35}{2}x^{-\frac{7}{2}}$.

Answer:

$-22x^{\frac{9}{2}}+\frac{35}{2}x^{-\frac{7}{2}}$