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Solve the rational inequality. Write the solution set in interval notation.

[tex]\[
\frac{-2}{1-x} \ \textless \ 8
\][/tex]

What is the solution set?

[tex]\(\square\)[/tex] (Type your answer in interval notation. Use integers or simplified fractions for any numbers in the expression.)

Sagot :

Let's solve the rational inequality [tex]\(\frac{-2}{1-x} < 8\)[/tex] step-by-step.

1. Rewrite the Inequality:
We start with:
[tex]\[ \frac{-2}{1-x} < 8 \][/tex]

2. Multiply Both Sides by the Denominator:
The inequality involves the fraction [tex]\(\frac{-2}{1-x}\)[/tex]. To eliminate the fraction, we multiply both sides of the inequality by [tex]\(1 - x\)[/tex]. Note that we must consider the sign of [tex]\(1 - x\)[/tex] because it affects the direction of the inequality.

- When [tex]\(1 - x > 0\)[/tex] (or [tex]\(x < 1\)[/tex]), we multiply both sides by [tex]\(1 - x\)[/tex], and the direction of the inequality remains the same:
[tex]\[ -2 < 8(1 - x) \][/tex]
- When [tex]\(1 - x < 0\)[/tex] (or [tex]\(x > 1\)[/tex]), we multiply both sides by [tex]\(1 - x\)[/tex], and the direction of the inequality reverses:
[tex]\[ -2 > 8(1 - x) \][/tex]

3. Consider Each Case Separately:

- Case 1: [tex]\(1 - x > 0\)[/tex] or [tex]\(x < 1\)[/tex]

[tex]\[ -2 < 8(1 - x) \][/tex]
Simplify the right side:
[tex]\[ -2 < 8 - 8x \][/tex]
Subtract 8 from both sides:
[tex]\[ -2 - 8 < -8x \][/tex]
Simplify further:
[tex]\[ -10 < -8x \][/tex]
Divide by -8 (remember to reverse the inequality sign):
[tex]\[ \frac{-10}{-8} > x \quad \text{or} \quad \frac{5}{4} > x \][/tex]
Therefore:
[tex]\[ x < \frac{5}{4} \][/tex]

- Case 2: [tex]\(1 - x < 0\)[/tex] or [tex]\(x > 1\)[/tex]

[tex]\[ -2 > 8(1 - x) \][/tex]
Simplify the right side:
[tex]\[ -2 > 8 - 8x \][/tex]
Subtract 8 from both sides:
[tex]\[ -2 - 8 > -8x \][/tex]
Simplify further:
[tex]\[ -10 > -8x \][/tex]
Divide by -8 (remember to reverse the inequality sign):
[tex]\[ \frac{-10}{-8} < x \quad \text{or} \quad \frac{5}{4} < x \][/tex]
Therefore:
[tex]\[ x > \frac{5}{4} \][/tex]

4. Combine the Results:
We have two cases:
[tex]\[ x < \frac{5}{4} \quad \text{and} \quad x > \frac{5}{4} \][/tex]
However, since [tex]\(x\)[/tex] cannot equal [tex]\(\frac{5}{4}\)[/tex] (it would make the denominator zero), we exclude [tex]\(\frac{5}{4}\)[/tex].

Therefore, combining the results gives us all real numbers but excluding [tex]\(x = \frac{5}{4}\)[/tex]:
[tex]\[ x \in (-\infty, \frac{5}{4}) \cup (\frac{5}{4}, \infty) \][/tex]

The Solution Set in Interval Notation:
[tex]\[ (-\infty, \frac{5}{4}) \cup (\frac{5}{4}, \infty) \][/tex]