Solve for x log base 8 of x+ log base 8 of 7x-1=1

$\log_{8} (x) + \log_{8} (7 x - 1) = 1$

Step 1

Simplify the left side.

Use the product property of logarithms, $\log_{b} (x) + \log_{b} (y) = \log_{b} (x y)$ .

$\log_{8} (x (7 x - 1)) = 1$

Simplify by multiplying through.

Apply the distributive property.

$\log_{8} (x (7 x) + x \cdot - 1) = 1$

Reorder.

Rewrite using the commutative property of multiplication.

$\log_{8} (7 x \cdot x + x \cdot - 1) = 1$

Move $- 1$ to the left of $x$ .

$\log_{8} (7 x \cdot x - 1 \cdot x) = 1$

Simplify each term.

Multiply $x$ by $x$ by adding the exponents.

Move $x$ .

$\log_{8} (7 (x \cdot x) - 1 \cdot x) = 1$

Multiply $x$ by $x$ .

$\log_{8} (7 x^{2} - 1 \cdot x) = 1$

Rewrite $- 1 x$ as $- x$ .

$\log_{8} (7 x^{2} - x) = 1$

Step 2

Rewrite $\log_{8} (7 x^{2} - x) = 1$ in exponential form using the definition of a logarithm. If $x$ and $b$ are positive real numbers and $b \neq 1$ , then $\log_{b} (x) = y$ is equivalent to $b^{y} = x$ .

$8^{1} = 7 x^{2} - x$

Step 3

Solve for $x$ .

Rewrite the equation as $7 x^{2} - x = 8^{1}$ .

$7 x^{2} - x = 8$

Subtract $8$ from both sides of the equation.

$7 x^{2} - x - 8 = 0$

Factor by grouping.

For a polynomial of the form $a x^{2} + b x + c$ , rewrite the middle term as a sum of two terms whose product is $a \cdot c = 7 \cdot - 8 = - 56$ and whose sum is $b = - 1$ .

Factor $- 1$ out of $- x$ .

$7 x^{2} - (x) - 8 = 0$

Rewrite $- 1$ as $7$ plus $- 8$

$7 x^{2} + (7 - 8) x - 8 = 0$

Apply the distributive property.

$7 x^{2} + 7 x - 8 x - 8 = 0$

Factor out the greatest common factor from each group.

Group the first two terms and the last two terms.

$(7 x^{2} + 7 x) - 8 x - 8 = 0$

Factor out the greatest common factor (GCF) from each group.

$7 x (x + 1) - 8 (x + 1) = 0$

Factor the polynomial by factoring out the greatest common factor, $x + 1$ .

$(x + 1) (7 x - 8) = 0$

If any individual factor on the left side of the equation is equal to $0$ , the entire expression will be equal to $0$ .

$x + 1 = 0$

$7 x - 8 = 0$

Set $x + 1$ equal to $0$ and solve for $x$ .

Set $x + 1$ equal to $0$ .

$x + 1 = 0$

Subtract $1$ from both sides of the equation.

$x = - 1$

Set $7 x - 8$ equal to $0$ and solve for $x$ .

Set $7 x - 8$ equal to $0$ .

$7 x - 8 = 0$

Solve $7 x - 8 = 0$ for $x$ .

Add $8$ to both sides of the equation.

$7 x = 8$

Divide each term in $7 x = 8$ by $7$ and simplify.

Divide each term in $7 x = 8$ by $7$ .

$\frac{7 x}{7} = \frac{8}{7}$

Simplify the left side.

Cancel the common factor of $7$ .

Cancel the common factor.

$\frac{7 x}{7} = \frac{8}{7}$

Divide $x$ by $1$ .

$x = \frac{8}{7}$

The final solution is all the values that make $(x + 1) (7 x - 8) = 0$ true.

$x = - 1, \frac{8}{7}$

Step 4

Exclude the solutions that do not make $\log_{8} (x) + \log_{8} (7 x - 1) = 1$ true.

$x = \frac{8}{7}$

Step 5

The result can be shown in multiple forms.

Exact Form:

$x = \frac{8}{7}$

Decimal Form:

$x = 1.\overline{142857}$

Mixed Number Form:

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

Solve for x log base 8 of x+ log base 8 of 7x-1=1

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