Math Problem Statement

Доведіть нерівності, якщо x — довільне дійсне число: 1) x^2 + 4 ≥ 4x; 2) 9x^2 ≥ 12x - 4.

Solution

The image contains two inequalities that you are asked to prove using the method of differences. Let's work through each one step by step.

1) Proving the inequality x2+44xx^2 + 4 \geq 4x:

Step 1: Rewrite the inequality. x2+44xx^2 + 4 \geq 4x Move all terms to one side: x24x+40x^2 - 4x + 4 \geq 0

Step 2: Factor the expression. Notice that the left-hand side is a perfect square: (x2)20(x - 2)^2 \geq 0

Step 3: Analyze the inequality. The square of any real number is always non-negative, i.e., (x2)20(x - 2)^2 \geq 0 for all xRx \in \mathbb{R}.

Therefore, the inequality holds for all real numbers xx, with equality when x=2x = 2.

2) Proving the inequality 9x212x49x^2 \geq 12x - 4:

Step 1: Rewrite the inequality. 9x212x49x^2 \geq 12x - 4 Move all terms to one side: 9x212x+409x^2 - 12x + 4 \geq 0

Step 2: Factor the quadratic expression. The expression can be factored as follows: (3x2)20(3x - 2)^2 \geq 0

Step 3: Analyze the inequality. Again, the square of any real number is always non-negative, i.e., (3x2)20(3x - 2)^2 \geq 0 for all xRx \in \mathbb{R}.

Thus, this inequality holds for all real numbers xx, with equality when x=23x = \frac{2}{3}.

Conclusion:

Both inequalities hold for all real numbers, with specific points where equality is achieved.


Would you like any additional explanations or details on these solutions?

Here are 5 follow-up questions related to this topic:

  1. How do you apply the method of differences to other inequalities?
  2. What are the key steps in factoring quadratic expressions?
  3. Why is a perfect square always non-negative?
  4. How can you check for the equality points in inequalities?
  5. How do these inequalities change if the constants are modified?

Tip: Always check if you can factor an expression, as this often simplifies solving inequalities.

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Math Problem Analysis

Mathematical Concepts

Algebra
Inequalities
Quadratic Equations

Formulas

(a - b)^2 ≥ 0
Quadratic inequality

Theorems

Non-negative property of squares
Factoring of quadratics

Suitable Grade Level

Grades 8-10