Find Where Undefined/Discontinuous 1/(x-4)-2/(x+5)=(2x-1)/(x^2+x-20)

$\frac{1}{x - 4} - \frac{2}{x + 5} = \frac{2 x - 1}{x^{2} + x - 20}$

Step 1

Subtract $\frac{2 x - 1}{x^{2} + x - 20}$ from both sides of the equation.

$\frac{1}{x - 4} - \frac{2}{x + 5} - \frac{2 x - 1}{x^{2} + x - 20} = 0$

Step 2

Simplify $\frac{1}{x - 4} - \frac{2}{x + 5} - \frac{2 x - 1}{x^{2} + x - 20}$ .

Factor $x^{2} + x - 20$ using the AC method.

Consider the form $x^{2} + b x + c$ . Find a pair of integers whose product is $c$ and whose sum is $b$ . In this case, whose product is $- 20$ and whose sum is $1$ .

$- 4, 5$

Write the factored form using these integers.

$\frac{1}{x - 4} - \frac{2}{x + 5} - \frac{2 x - 1}{(x - 4) (x + 5)} = 0$

To write $\frac{1}{x - 4}$ as a fraction with a common denominator, multiply by $\frac{x + 5}{x + 5}$ .

$\frac{1}{x - 4} \cdot \frac{x + 5}{x + 5} - \frac{2}{x + 5} - \frac{2 x - 1}{(x - 4) (x + 5)} = 0$

To write $- \frac{2}{x + 5}$ as a fraction with a common denominator, multiply by $\frac{x - 4}{x - 4}$ .

$\frac{1}{x - 4} \cdot \frac{x + 5}{x + 5} - \frac{2}{x + 5} \cdot \frac{x - 4}{x - 4} - \frac{2 x - 1}{(x - 4) (x + 5)} = 0$

Write each expression with a common denominator of $(x - 4) (x + 5)$ , by multiplying each by an appropriate factor of $1$ .

Multiply $\frac{1}{x - 4}$ by $\frac{x + 5}{x + 5}$ .

$\frac{x + 5}{(x - 4) (x + 5)} - \frac{2}{x + 5} \cdot \frac{x - 4}{x - 4} - \frac{2 x - 1}{(x - 4) (x + 5)} = 0$

Multiply $\frac{2}{x + 5}$ by $\frac{x - 4}{x - 4}$ .

$\frac{x + 5}{(x - 4) (x + 5)} - \frac{2 (x - 4)}{(x + 5) (x - 4)} - \frac{2 x - 1}{(x - 4) (x + 5)} = 0$

Reorder the factors of $(x - 4) (x + 5)$ .

$\frac{x + 5}{(x + 5) (x - 4)} - \frac{2 (x - 4)}{(x + 5) (x - 4)} - \frac{2 x - 1}{(x - 4) (x + 5)} = 0$

Combine the numerators over the common denominator.

$\frac{x + 5 - 2 (x - 4)}{(x + 5) (x - 4)} - \frac{2 x - 1}{(x - 4) (x + 5)} = 0$

Combine the numerators over the common denominator.

$\frac{x + 5 - 2 (x - 4) - (2 x - 1)}{(x + 5) (x - 4)} = 0$

Simplify each term.

Apply the distributive property.

$\frac{x + 5 - 2 x - 2 \cdot - 4 - (2 x - 1)}{(x + 5) (x - 4)} = 0$

Multiply $- 2$ by $- 4$ .

$\frac{x + 5 - 2 x + 8 - (2 x - 1)}{(x + 5) (x - 4)} = 0$

Apply the distributive property.

$\frac{x + 5 - 2 x + 8 - (2 x) - - 1}{(x + 5) (x - 4)} = 0$

Multiply $2$ by $- 1$ .

$\frac{x + 5 - 2 x + 8 - 2 x - - 1}{(x + 5) (x - 4)} = 0$

Multiply $- 1$ by $- 1$ .

$\frac{x + 5 - 2 x + 8 - 2 x + 1}{(x + 5) (x - 4)} = 0$

Subtract $2 x$ from $x$ .

$\frac{- x + 5 + 8 - 2 x + 1}{(x + 5) (x - 4)} = 0$

Subtract $2 x$ from $- x$ .

$\frac{- 3 x + 5 + 8 + 1}{(x + 5) (x - 4)} = 0$

Add $5$ and $8$ .

$\frac{- 3 x + 13 + 1}{(x + 5) (x - 4)} = 0$

Add $13$ and $1$ .

$\frac{- 3 x + 14}{(x + 5) (x - 4)} = 0$

Factor $- 1$ out of $- 3 x$ .

$\frac{- (3 x) + 14}{(x + 5) (x - 4)} = 0$

Rewrite $14$ as $- 1 (- 14)$ .

$\frac{- (3 x) - 1 (- 14)}{(x + 5) (x - 4)} = 0$

Factor $- 1$ out of $- (3 x) - 1 (- 14)$ .

$\frac{- (3 x - 14)}{(x + 5) (x - 4)} = 0$

Rewrite $- (3 x - 14)$ as $- 1 (3 x - 14)$ .

$\frac{- 1 (3 x - 14)}{(x + 5) (x - 4)} = 0$

Move the negative in front of the fraction.

$- \frac{3 x - 14}{(x + 5) (x - 4)} = 0$

Step 3

Set the denominator in $\frac{3 x - 14}{(x + 5) (x - 4)}$ equal to $0$ to find where the expression is undefined.

$(x + 5) (x - 4) = 0$

Step 4

Solve for $x$ .

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

$x + 5 = 0$

$x - 4 = 0$

Set $x + 5$ equal to $0$ and solve for $x$ .

Set $x + 5$ equal to $0$ .

$x + 5 = 0$

Subtract $5$ from both sides of the equation.

$x = - 5$

Set $x - 4$ equal to $0$ and solve for $x$ .

Set $x - 4$ equal to $0$ .

$x - 4 = 0$

Add $4$ to both sides of the equation.

$x = 4$

The final solution is all the values that make $(x + 5) (x - 4) = 0$ true.

$x = - 5, 4$

Step 5

The equation is undefined where the denominator equals $0$ , the argument of a square root is less than $0$ , or the argument of a logarithm is less than or equal to $0$ .

$x = - 5, x = 4$

Step 6

Find Where Undefined/Discontinuous 1/(x-4)-2/(x+5)=(2x-1)/(x^2+x-20)

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