Precalculus Examples

$\log (x + 7) - \log (2) = \log (x)$

Step 1

Use the quotient property of logarithms, $\log_{b} (x) - \log_{b} (y) = \log_{b} (\frac{x}{y})$ .

$\log (\frac{x + 7}{2}) = \log (x)$

Step 2

For the equation to be equal, the argument of the logarithms on both sides of the equation must be equal.

$\frac{x + 7}{2} = x$

Step 3

Solve for $x$ .

Tap for more steps...

Step 3.1

Multiply both sides by $2$ .

$\frac{x + 7}{2} \cdot 2 = x \cdot 2$

Step 3.2

Simplify.

Tap for more steps...

Step 3.2.1

Simplify the left side.

Tap for more steps...

Step 3.2.1.1

Cancel the common factor of $2$ .

Tap for more steps...

Step 3.2.1.1.1

Cancel the common factor.

$\frac{x + 7}{2} \cdot 2 = x \cdot 2$

Step 3.2.1.1.2

Rewrite the expression.

$x + 7 = x \cdot 2$

Step 3.2.2

Simplify the right side.

Tap for more steps...

Step 3.2.2.1

Move $2$ to the left of $x$ .

$x + 7 = 2 x$

Step 3.3

Solve for $x$ .

Tap for more steps...

Step 3.3.1

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

Tap for more steps...

Step 3.3.1.1

Subtract $2 x$ from both sides of the equation.

$x + 7 - 2 x = 0$

Step 3.3.1.2

Subtract $2 x$ from $x$ .

$- x + 7 = 0$

Step 3.3.2

Subtract $7$ from both sides of the equation.

$- x = - 7$

Step 3.3.3

Divide each term in $- x = - 7$ by $- 1$ and simplify.

Tap for more steps...

Step 3.3.3.1

Divide each term in $- x = - 7$ by $- 1$ .

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

Step 3.3.3.2

Simplify the left side.

Tap for more steps...

Step 3.3.3.2.1

Dividing two negative values results in a positive value.

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

Step 3.3.3.2.2

Divide $x$ by $1$ .

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

Step 3.3.3.3

Simplify the right side.

Tap for more steps...

Step 3.3.3.3.1

Divide $- 7$ by $- 1$ .

$x = 7$