Subjects algebra

Absolute Value Inequality Deaa8F

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1. **State the problem:** Solve the inequality $$\left|\frac{x+9}{x-9}\right| \le 2.$$\n\n2. **Rewrite the absolute value inequality:** This means \(-2 \le \frac{x+9}{x-9} \le 2\).\n\n3. **Solve the left inequality:** \n$$-2 \le \frac{x+9}{x-9}$$\nMultiply both sides by \(x-9\), but consider the sign of \(x-9\) because it affects the inequality direction.\n\n- For \(x > 9\), multiply without changing inequality:\n$$-2(x-9) \le x+9$$\n$$-2x + 18 \le x + 9$$\n$$18 - 9 \le x + 2x$$\n$$9 \le 3x$$\n$$x \ge 3$$\n\n- For \(x < 9\), multiply and reverse inequality:\n$$-2(x-9) \ge x+9$$\n$$-2x + 18 \ge x + 9$$\n$$18 - 9 \ge x + 2x$$\n$$9 \ge 3x$$\n$$x \le 3$$\n\n4. **Solve the right inequality:** \n$$\frac{x+9}{x-9} \le 2$$\nMultiply both sides by \(x-9\), again considering sign:\n\n- For \(x > 9\):\n$$x+9 \le 2(x-9)$$\n$$x + 9 \le 2x - 18$$\n$$9 + 18 \le 2x - x$$\n$$27 \le x$$\n\n- For \(x < 9\):\n$$x+9 \ge 2(x-9)$$\n$$x + 9 \ge 2x - 18$$\n$$9 + 18 \ge 2x - x$$\n$$27 \ge x$$\n\n5. **Combine intervals and consider domain:** \nThe expression is undefined at \(x=9\).\n\n- For \(x > 9\), from left inequality: \(x \ge 3\) (always true), from right inequality: \(x \ge 27\). So for \(x > 9\), solution is \(x \ge 27\).\n\n- For \(x < 9\), from left inequality: \(x \le 3\), from right inequality: \(x \le 27\) (always true). So for \(x < 9\), solution is \(x \le 3\).\n\n6. **Final solution:** \n$$(-\infty, 3] \cup [27, \infty)$$\n\n7. **Summary:** The values of \(x\) that satisfy the inequality are all real numbers less than or equal to 3, and all real numbers greater than or equal to 27, excluding \(x=9\) where the expression is undefined.