Calculus Examples

$y = \frac{7 x}{x - 1}$

Step 1

Differentiate both sides of the equation.

$\frac{d}{d x} (y) = \frac{d}{d x} (\frac{7 x}{x - 1})$

Step 2

The derivative of $y$ with respect to $x$ is $y'$ .

$y'$

Step 3

Differentiate the right side of the equation.

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Step 3.1

Since $7$ is constant with respect to $x$ , the derivative of $\frac{7 x}{x - 1}$ with respect to $x$ is $7 \frac{d}{d x} [\frac{x}{x - 1}]$ .

$7 \frac{d}{d x} [\frac{x}{x - 1}]$

Step 3.2

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 $g (x) = x - 1$ .

$7 \frac{(x - 1) \frac{d}{d x} [x] - x \frac{d}{d x} [x - 1]}{{(x - 1)}^{2}}$

Step 3.3

Differentiate.

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Step 3.3.1

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

$7 \frac{(x - 1) \cdot 1 - x \frac{d}{d x} [x - 1]}{{(x - 1)}^{2}}$

Step 3.3.2

Multiply $x - 1$ by $1$ .

$7 \frac{x - 1 - x \frac{d}{d x} [x - 1]}{{(x - 1)}^{2}}$

Step 3.3.3

By the Sum Rule, the derivative of $x - 1$ with respect to $x$ is $\frac{d}{d x} [x] + \frac{d}{d x} [- 1]$ .

$7 \frac{x - 1 - x (\frac{d}{d x} [x] + \frac{d}{d x} [- 1])}{{(x - 1)}^{2}}$

Step 3.3.4

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

$7 \frac{x - 1 - x (1 + \frac{d}{d x} [- 1])}{{(x - 1)}^{2}}$

Step 3.3.5

Since $- 1$ is constant with respect to $x$ , the derivative of $- 1$ with respect to $x$ is $0$ .

$7 \frac{x - 1 - x (1 + 0)}{{(x - 1)}^{2}}$

Step 3.3.6

Simplify terms.

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Step 3.3.6.1

Add $1$ and $0$ .

$7 \frac{x - 1 - x \cdot 1}{{(x - 1)}^{2}}$

Step 3.3.6.2

Multiply $- 1$ by $1$ .

$7 \frac{x - 1 - x}{{(x - 1)}^{2}}$

Step 3.3.6.3

Subtract $x$ from $x$ .

$7 \frac{0 - 1}{{(x - 1)}^{2}}$

Step 3.3.6.4

Simplify the expression.

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Step 3.3.6.4.1

Subtract $1$ from $0$ .

$7 \frac{- 1}{{(x - 1)}^{2}}$

Step 3.3.6.4.2

Move the negative in front of the fraction.

$7 (- \frac{1}{{(x - 1)}^{2}})$

Step 3.3.6.4.3

Multiply $- 1$ by $7$ .

$- 7 \frac{1}{{(x - 1)}^{2}}$

Step 3.3.6.5

Combine $- 7$ and $\frac{1}{{(x - 1)}^{2}}$ .

$\frac{- 7}{{(x - 1)}^{2}}$

Step 3.3.6.6

Move the negative in front of the fraction.

$- \frac{7}{{(x - 1)}^{2}}$

Step 4

Reform the equation by setting the left side equal to the right side.

$y' = - \frac{7}{{(x - 1)}^{2}}$

Step 5

Replace $y'$ with $\frac{d y}{d x}$ .

$\frac{d y}{d x} = - \frac{7}{{(x - 1)}^{2}}$