Calculus Examples

$y = \frac{x}{x - 9}$

Step 1

Differentiate using the Quotient Rule which states that $\frac{d}{d x} [\frac{f (x)}{g (x)}]$ is $\frac{g (x) \frac{d}{d x} [f (x)] - f (x) \frac{d}{d x} [g (x)]}{{g (x)}^{2}}$ where $f (x) = x$ and $g (x) = x - 9$ .

$\frac{(x - 9) \frac{d}{d x} [x] - x \frac{d}{d x} [x - 9]}{{(x - 9)}^{2}}$

Step 2

Differentiate.

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Step 2.1

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$\frac{(x - 9) \cdot 1 - x \frac{d}{d x} [x - 9]}{{(x - 9)}^{2}}$

Step 2.2

Multiply $x - 9$ by $1$ .

$\frac{x - 9 - x \frac{d}{d x} [x - 9]}{{(x - 9)}^{2}}$

Step 2.3

By the Sum Rule, the derivative of $x - 9$ with respect to $x$ is $\frac{d}{d x} [x] + \frac{d}{d x} [- 9]$ .

$\frac{x - 9 - x (\frac{d}{d x} [x] + \frac{d}{d x} [- 9])}{{(x - 9)}^{2}}$

Step 2.4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$\frac{x - 9 - x (1 + \frac{d}{d x} [- 9])}{{(x - 9)}^{2}}$

Step 2.5

Since $- 9$ is constant with respect to $x$ , the derivative of $- 9$ with respect to $x$ is $0$ .

$\frac{x - 9 - x (1 + 0)}{{(x - 9)}^{2}}$

Step 2.6

Simplify by adding terms.

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Step 2.6.1

Add $1$ and $0$ .

$\frac{x - 9 - x \cdot 1}{{(x - 9)}^{2}}$

Step 2.6.2

Multiply $- 1$ by $1$ .

$\frac{x - 9 - x}{{(x - 9)}^{2}}$

Step 2.6.3

Subtract $x$ from $x$ .

$\frac{0 - 9}{{(x - 9)}^{2}}$

Step 2.6.4

Simplify the expression.

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Step 2.6.4.1

Subtract $9$ from $0$ .

$\frac{- 9}{{(x - 9)}^{2}}$

Step 2.6.4.2

Move the negative in front of the fraction.

$- \frac{9}{{(x - 9)}^{2}}$