Find the Derivative - d/dx log of |5-7x|

$\log (| 5 - 7 x |)$

Step 1

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \log (x)$ and $g (x) = | 5 - 7 x |$ .

To apply the Chain Rule, set $u_{1}$ as $| 5 - 7 x |$ .

$\frac{d}{d u_{1}} [\log (u_{1})] \frac{d}{d x} [| 5 - 7 x |]$

The derivative of $\log (u_{1})$ with respect to $u_{1}$ is $\frac{1}{u_{1} \ln (10)}$ .

$\frac{1}{u_{1} \ln (10)} \frac{d}{d x} [| 5 - 7 x |]$

Replace all occurrences of $u_{1}$ with $| 5 - 7 x |$ .

$\frac{1}{| 5 - 7 x | \ln (10)} \frac{d}{d x} [| 5 - 7 x |]$

Step 2

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = | x |$ and $g (x) = 5 - 7 x$ .

To apply the Chain Rule, set $u_{2}$ as $5 - 7 x$ .

$\frac{1}{| 5 - 7 x | \ln (10)} (\frac{d}{d u_{2}} [| u_{2} |] \frac{d}{d x} [5 - 7 x])$

The derivative of $| u_{2} |$ with respect to $u_{2}$ is $\frac{u_{2}}{| u_{2} |}$ .

$\frac{1}{| 5 - 7 x | \ln (10)} (\frac{u_{2}}{| u_{2} |} \frac{d}{d x} [5 - 7 x])$

Replace all occurrences of $u_{2}$ with $5 - 7 x$ .

$\frac{1}{| 5 - 7 x | \ln (10)} (\frac{5 - 7 x}{| 5 - 7 x |} \frac{d}{d x} [5 - 7 x])$

Step 3

Multiply $\frac{5 - 7 x}{| 5 - 7 x |}$ by $\frac{1}{| 5 - 7 x | \ln (10)}$ .

$\frac{5 - 7 x}{| 5 - 7 x | (| 5 - 7 x | \ln (10))} \frac{d}{d x} [5 - 7 x]$

Step 4

To multiply absolute values, multiply the terms inside each absolute value.

$\frac{5 - 7 x}{| (5 - 7 x) (5 - 7 x) | \ln (10)} \frac{d}{d x} [5 - 7 x]$

Step 5

Raise $5 - 7 x$ to the power of $1$ .

$\frac{5 - 7 x}{| {(5 - 7 x)}^{1} (5 - 7 x) | \ln (10)} \frac{d}{d x} [5 - 7 x]$

Step 6

Raise $5 - 7 x$ to the power of $1$ .

$\frac{5 - 7 x}{| {(5 - 7 x)}^{1} {(5 - 7 x)}^{1} | \ln (10)} \frac{d}{d x} [5 - 7 x]$

Step 7

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{5 - 7 x}{| {(5 - 7 x)}^{1 + 1} | \ln (10)} \frac{d}{d x} [5 - 7 x]$

Step 8

Add $1$ and $1$ .

$\frac{5 - 7 x}{| {(5 - 7 x)}^{2} | \ln (10)} \frac{d}{d x} [5 - 7 x]$

Step 9

By the Sum Rule, the derivative of $5 - 7 x$ with respect to $x$ is $\frac{d}{d x} [5] + \frac{d}{d x} [- 7 x]$ .

$\frac{5 - 7 x}{| {(5 - 7 x)}^{2} | \ln (10)} (\frac{d}{d x} [5] + \frac{d}{d x} [- 7 x])$

Step 10

Since $5$ is constant with respect to $x$ , the derivative of $5$ with respect to $x$ is $0$ .

$\frac{5 - 7 x}{| {(5 - 7 x)}^{2} | \ln (10)} (0 + \frac{d}{d x} [- 7 x])$

Step 11

Add $0$ and $\frac{d}{d x} [- 7 x]$ .

$\frac{5 - 7 x}{| {(5 - 7 x)}^{2} | \ln (10)} \frac{d}{d x} [- 7 x]$

Step 12

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

$\frac{5 - 7 x}{| {(5 - 7 x)}^{2} | \ln (10)} (- 7 \frac{d}{d x} [x])$

Step 13

Combine fractions.

Combine $- 7$ and $\frac{5 - 7 x}{| {(5 - 7 x)}^{2} | \ln (10)}$ .

$\frac{- 7 (5 - 7 x)}{| {(5 - 7 x)}^{2} | \ln (10)} \frac{d}{d x} [x]$

Move the negative in front of the fraction.

$- \frac{(7) (5 - 7 x)}{| {(5 - 7 x)}^{2} | \ln (10)} \frac{d}{d x} [x]$

Step 14

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

$- \frac{7 (5 - 7 x)}{| {(5 - 7 x)}^{2} | \ln (10)} \cdot 1$

Step 15

Multiply $- 1$ by $1$ .

$- \frac{7 (5 - 7 x)}{| {(5 - 7 x)}^{2} | \ln (10)}$

Find the Derivative - d/dx log of |5-7x|

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