Question

Difficulty: Very hardLinear and Quadratic Inequalities

Which of the following represents the complete set of real values of xx that satisfy the inequality x2x6x10\frac{x^2 - x - 6}{x - 1} \le 0?

  1. x2x \le -2 or 1<x31 < x \le 3Answer
  2. B
    x2x \le -2 or 1x31 \le x \le 3
  3. C
    2x<1-2 \le x < 1 or x3x \ge 3
  4. D
    2x3-2 \le x \le 3 with x1x \neq 1

Answer

The complete solution set is x2x \le -2 or 1<x31 < x \le 3.
The expression (x3)(x+2)x1\frac{(x-3)(x+2)}{x-1} evaluates to a non-positive value (0\le 0) when the numerator and denominator have opposite signs or when the numerator is zero. Evaluating across the critical boundaries x=2,1,3x = -2, 1, 3 while excluding x=1x = 1 yields the solution set x2x \le -2 or 1<x31 < x \le 3.

Step-by-Step Solution

1
Factor the quadratic numerator and state the domain restriction.
The numerator factors as x2x6=(x3)(x+2)x^2 - x - 6 = (x - 3)(x + 2), giving the rational inequality (x3)(x+2)x10\frac{(x - 3)(x + 2)}{x - 1} \le 0 with x1x \neq 1.
Factoring isolates the critical boundary points where the expression can change sign.
2
Identify all critical numbers.
The critical values are x=2x = -2, x=1x = 1, and x=3x = 3.
These points partition the real number line into sub-intervals.
3
Test points in each interval to determine the sign of the rational function f(x)=(x3)(x+2)x1f(x) = \frac{(x - 3)(x + 2)}{x - 1}.
For x<2x < -2, f(x)0f(x) \le 0; for 2<x<1-2 < x < 1, f(x)>0f(x) > 0; for 1<x<31 < x < 3, f(x)0f(x) \le 0; for x>3x > 3, f(x)>0f(x) > 0.
Determining where the function is negative or zero identifies the regions satisfying 0\le 0.
4
Combine intervals and include non-undefined endpoints.
Endpoints x=2x = -2 and x=3x = 3 make the numerator zero (included), while x=1x = 1 makes the denominator zero (excluded). Thus, x2x \le -2 or 1<x31 < x \le 3.
Division by zero must be excluded from the solution set.

Key Concept

Solving rational inequalities by finding critical values, using test intervals, and respecting domain restrictions.
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