Math Problem Statement

2x-1/x+3>=0

Solution

To solve the inequality 2x1x+30\frac{2x - 1}{x + 3} \geq 0, we will follow a series of steps.

Step 1: Find the critical points

The critical points are values where the expression equals zero or is undefined. These occur where the numerator or denominator equals zero.

  • Numerator: Set 2x1=02x - 1 = 0 2x=1x=122x = 1 \quad \Rightarrow \quad x = \frac{1}{2}
  • Denominator: Set x+3=0x + 3 = 0 x=3x = -3 Thus, the critical points are x=12x = \frac{1}{2} and x=3x = -3.

Step 2: Analyze the sign of the expression

We need to examine the sign of 2x1x+3\frac{2x - 1}{x + 3} in the intervals formed by the critical points. These intervals are:

  1. (,3)(-\infty, -3)
  2. (3,12)(-3, \frac{1}{2})
  3. (12,)(\frac{1}{2}, \infty)

We will test a point in each of these intervals to determine the sign of the expression.

Interval 1: (,3)(-\infty, -3)

Choose x=4x = -4: 2(4)14+3=811=91=9(positive)\frac{2(-4) - 1}{-4 + 3} = \frac{-8 - 1}{-1} = \frac{-9}{-1} = 9 \quad (\text{positive})

Interval 2: (3,12)(-3, \frac{1}{2})

Choose x=0x = 0: 2(0)10+3=13(negative)\frac{2(0) - 1}{0 + 3} = \frac{-1}{3} \quad (\text{negative})

Interval 3: (12,)(\frac{1}{2}, \infty)

Choose x=1x = 1: 2(1)11+3=214=14(positive)\frac{2(1) - 1}{1 + 3} = \frac{2 - 1}{4} = \frac{1}{4} \quad (\text{positive})

Step 3: Consider the equality and undefined points

  • At x=12x = \frac{1}{2}, the expression equals zero: 2x1x+3=0\frac{2x - 1}{x + 3} = 0, so x=12x = \frac{1}{2} is part of the solution.
  • At x=3x = -3, the expression is undefined, so x=3x = -3 is not part of the solution.

Step 4: Construct the solution

We are looking for where the expression is greater than or equal to zero. From our analysis:

  • The expression is positive in the intervals (,3)(-\infty, -3) and (12,)(\frac{1}{2}, \infty).
  • The expression equals zero at x=12x = \frac{1}{2}.

Thus, the solution is: x(,3)[12,)x \in (-\infty, -3) \cup \left[ \frac{1}{2}, \infty \right) However, remember that x=3x = -3 is excluded since the expression is undefined there.

Final Solution:

x(,3)[12,)x \in (-\infty, -3) \cup \left[ \frac{1}{2}, \infty \right)

Would you like further clarification or a step-by-step breakdown of the solution? Here are some related questions you could explore:

  1. How would the solution change if the inequality were strict, i.e., 2x1x+3>0\frac{2x - 1}{x + 3} > 0?
  2. What happens if we have a similar inequality with different constants in the numerator and denominator?
  3. How do we approach solving rational inequalities with higher-degree polynomials?
  4. Can the sign analysis method be used for all rational inequalities?
  5. How can we graph the inequality 2x1x+30\frac{2x - 1}{x + 3} \geq 0 to visually verify the solution?

Tip: For rational inequalities, always check where the expression is undefined (denominator zero) and where the numerator equals zero to correctly identify the critical points.

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Math Problem Analysis

Mathematical Concepts

Rational Inequalities
Sign Analysis
Critical Points

Formulas

(2x - 1) / (x + 3) >= 0

Theorems

Sign analysis for rational expressions
Critical point analysis

Suitable Grade Level

Grades 9-11