Math Problem Statement

Solve (x - 2)(x + 3) / (-x + 4) < 0 by filling in the sign chart with a - where you want to indicate negative and a + where you want to indicate positive. Use -inf for −∞ and inf for ∞.

Solution

Let's walk through how to solve this inequality and fill out the sign chart.

Problem:

We are given the inequality: (x2)(x+3)x+4<0\frac{(x - 2)(x + 3)}{-x + 4} < 0

The goal is to determine where this rational expression is negative and positive by analyzing the sign changes across different intervals, based on critical points.


Step 1: Find the critical points

The critical points occur where:

  • The numerator (x2)(x+3)=0(x - 2)(x + 3) = 0

    • x=2x = 2
    • x=3x = -3
  • The denominator x+4=0-x + 4 = 0

    • x=4x = 4

These points split the real number line into the following intervals:

  1. (,3)(-\infty, -3)
  2. (3,2)(-3, 2)
  3. (2,4)(2, 4)
  4. (4,)(4, \infty)

Note: At x=4x = 4, the expression is undefined since the denominator becomes 0.


Step 2: Choose test points within each interval

We’ll test the signs of the factors and the overall expression at points within each interval:

  • In (,3)(-\infty, -3), use x=4x = -4
  • In (3,2)(-3, 2), use x=0x = 0
  • In (2,4)(2, 4), use x=3x = 3
  • In (4,)(4, \infty), use x=5x = 5

Step 3: Analyze the signs

Let's check the sign of each factor in the expression for the chosen points.

Intervalx+3x + 3x2x - 2x+4-x + 4(x2)(x+3)x+4\frac{(x - 2)(x + 3)}{-x + 4}
(,3)(- \infty, -3)--++++
(3,2)(-3, 2)++-++-
(2,4)(2, 4)++++++++
(4,)(4, \infty)++++--

Step 4: Identify where the expression is negative

We are interested in where the expression is less than 0.

From the table:

  • The expression is negative in the intervals (3,2)(-3, 2) and (4,)(4, \infty).

Step 5: Write the solution

Since the expression is undefined at x=4x = 4, we exclude it from the solution. The final solution is:

(3,2)(4,)(-3, 2) \cup (4, \infty)


Final Answer:

Now you can fill the sign chart accordingly:

  1. For x+3x + 3:

    • Negative in (,3)(- \infty, -3)
    • Positive in (3,2)(-3, 2), (2,4)(2, 4), and (4,)(4, \infty)
  2. For x2x - 2:

    • Negative in (,2)(- \infty, 2)
    • Positive in (2,)(2, \infty)
  3. For x+4-x + 4:

    • Positive in (,4)(- \infty, 4)
    • Negative in (4,)(4, \infty)
  4. For the overall expression (x2)(x+3)x+4\frac{(x - 2)(x + 3)}{-x + 4}:

    • Positive in (,3)(- \infty, -3) and (2,4)(2, 4)
    • Negative in (3,2)(-3, 2) and (4,)(4, \infty)

Would you like further details on how to fill the chart?
Here are five related questions to explore:

  1. How do we handle rational inequalities involving multiple critical points?
  2. What is the role of test points in sign charts?
  3. Why is the expression undefined at x=4x = 4?
  4. How would the solution change if the inequality were 0\geq 0?
  5. What happens if the denominator has multiple roots?

Tip: Always be mindful of where the expression is undefined when dealing with rational inequalities!

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Math Problem Analysis

Mathematical Concepts

Inequalities
Sign Analysis
Rational Functions

Formulas

(x - 2)(x + 3) / (-x + 4) < 0

Theorems

Critical points in rational inequalities
Sign analysis across intervals

Suitable Grade Level

Grades 10-12