Math Problem Statement

x^3-x> or equal to 0

Solution

To solve the inequality x3x0x^3 - x \geq 0, let's follow these steps:

Step 1: Factor the inequality

First, rewrite the inequality:

x3x0x^3 - x \geq 0

Factor the expression on the left-hand side:

x(x21)0x(x^2 - 1) \geq 0

Now, notice that x21x^2 - 1 is a difference of squares:

x(x1)(x+1)0x(x - 1)(x + 1) \geq 0

Step 2: Find the critical points

The critical points occur when any of the factors are equal to zero. Set each factor to zero:

x=0,x1=0    x=1,x+1=0    x=1x = 0, \quad x - 1 = 0 \implies x = 1, \quad x + 1 = 0 \implies x = -1

So, the critical points are x=1x = -1, x=0x = 0, and x=1x = 1.

Step 3: Analyze the sign of the expression

We now analyze the sign of the expression x(x1)(x+1)x(x - 1)(x + 1) in the intervals determined by the critical points: (,1)(-\infty, -1), (1,0)(-1, 0), (0,1)(0, 1), and (1,)(1, \infty).

  1. For x(,1)x \in (-\infty, -1):
    Each factor is negative, so the product is negative.

    ()()()=(-)(-)(-) = - Therefore, x(x1)(x+1)<0x(x - 1)(x + 1) < 0.

  2. For x(1,0)x \in (-1, 0):
    x+1x + 1 is positive, while xx and x1x - 1 are negative, so the product is positive.

    ()()(+)=+(-)(-)(+) = + Therefore, x(x1)(x+1)>0x(x - 1)(x + 1) > 0.

  3. For x(0,1)x \in (0, 1):
    xx is positive, but x1x - 1 is negative and x+1x + 1 is positive, so the product is negative.

    (+)()(+)=(+)(-)(+) = - Therefore, x(x1)(x+1)<0x(x - 1)(x + 1) < 0.

  4. For x(1,)x \in (1, \infty):
    All the factors are positive, so the product is positive.

    (+)(+)(+)=+(+)(+)(+) = + Therefore, x(x1)(x+1)>0x(x - 1)(x + 1) > 0.

Step 4: Include critical points

At x=1x = -1, x=0x = 0, and x=1x = 1, the expression equals zero:

x(x1)(x+1)=0x(x - 1)(x + 1) = 0

Step 5: Write the solution

The inequality x(x1)(x+1)0x(x - 1)(x + 1) \geq 0 holds when the expression is either positive or zero. From our sign analysis, this happens in the intervals:

x[1,0][1,)x \in [-1, 0] \cup [1, \infty)

Thus, the solution to the inequality is:

x[1,0][1,)x \in [-1, 0] \cup [1, \infty)

Would you like further details or have any questions?


Here are five related questions to explore further:

  1. How would the solution change if the inequality were strict (x3x>0x^3 - x > 0)?
  2. What is the solution to the inequality x2x0x^2 - x \geq 0?
  3. Can you solve a similar inequality for x4x0x^4 - x \geq 0?
  4. How would you solve x32x0x^3 - 2x \geq 0?
  5. Can you solve the equation x3x=0x^3 - x = 0 for its exact roots?

Tip: When factoring polynomials, always check for differences of squares and common factors!

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Math Problem Analysis

Mathematical Concepts

Algebra
Inequalities
Cubic Functions
Factoring

Formulas

Factoring a cubic equation x(x - 1)(x + 1)

Theorems

Difference of squares

Suitable Grade Level

Grades 9-11