Examples

$f (x) = x + 4$ , $f (x) = 3 x$

Step 1

Substitute $3 x$ for $f (x)$ .

$3 x = x + 4$

Step 2

Solve for $x$ .

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Step 2.1

Move all terms containing $x$ to the left side of the equation.

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Step 2.1.1

Subtract $x$ from both sides of the equation.

$3 x - x = 4$

Step 2.1.2

Subtract $x$ from $3 x$ .

$2 x = 4$

Step 2.2

Divide each term in $2 x = 4$ by $2$ and simplify.

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Step 2.2.1

Divide each term in $2 x = 4$ by $2$ .

$\frac{2 x}{2} = \frac{4}{2}$

Step 2.2.2

Simplify the left side.

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Step 2.2.2.1

Cancel the common factor of $2$ .

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Step 2.2.2.1.1

Cancel the common factor.

$\frac{2 x}{2} = \frac{4}{2}$

Step 2.2.2.1.2

Divide $x$ by $1$ .

$x = \frac{4}{2}$

Step 2.2.3

Simplify the right side.

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Step 2.2.3.1

Divide $4$ by $2$ .

$x = 2$

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