Math Problem Statement

x² - x < 6

Solution

To solve the inequality x2x<6x^2 - x < 6, we start by rewriting it as a standard quadratic inequality:

x2x6<0x^2 - x - 6 < 0

Step 1: Factor the Quadratic Expression

First, factor the expression on the left:

x2x6=(x3)(x+2)x^2 - x - 6 = (x - 3)(x + 2)

Step 2: Determine the Critical Points

Set each factor equal to zero to find the critical points:

x3=0    x=3x - 3 = 0 \implies x = 3

x+2=0    x=2x + 2 = 0 \implies x = -2

Step 3: Test Intervals Around the Critical Points

The critical points divide the number line into three intervals:

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

We need to test each interval to determine where the inequality holds.

Interval 1: (,2)(-\infty, -2)
Choose a test point, say x=3x = -3:

(x3)(x+2)=(33)(3+2)=(6)(1)=6(x - 3)(x + 2) = (-3 - 3)(-3 + 2) = (-6)(-1) = 6

Since 6>06 > 0, this interval does not satisfy the inequality.

Interval 2: (2,3)(-2, 3)
Choose a test point, say x=0x = 0:

(x3)(x+2)=(03)(0+2)=(3)(2)=6(x - 3)(x + 2) = (0 - 3)(0 + 2) = (-3)(2) = -6

Since 6<0-6 < 0, this interval satisfies the inequality.

Interval 3: (3,)(3, \infty)
Choose a test point, say x=4x = 4:

(x3)(x+2)=(43)(4+2)=(1)(6)=6(x - 3)(x + 2) = (4 - 3)(4 + 2) = (1)(6) = 6

Since 6>06 > 0, this interval does not satisfy the inequality.

Step 4: Combine the Results

The solution to the inequality is:

x(2,3)x \in (-2, 3)

Final Answer

x(2,3)\boxed{x \in (-2, 3)}

Would you like more details or have any questions? Here are some related questions:

  1. How do you solve quadratic inequalities using a number line?
  2. What happens if the inequality is x2x6x^2 - x \leq 6?
  3. How can you verify the solution graphically?
  4. What other methods can be used to solve quadratic inequalities?
  5. How does the sign of the inequality affect the solution?

Tip: Always check your critical points to ensure they are correctly placed on the number line and test each interval to confirm the inequality's behavior!

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Inequalities
Factoring

Formulas

Quadratic equation formula ax^2 + bx + c = 0
Factored form of quadratic equations

Theorems

Sign Analysis for Inequalities
Factoring Theorem

Suitable Grade Level

Grades 9-10