Math Problem Statement
Prouve that for every x and y superior to 1 : sqr(x) +sqr(y) inferior to sqr(xy)
Solution
We are tasked with proving the inequality:
for all and .
Step 1: Restate the inequality
The given inequality is: We will first manipulate this inequality algebraically.
Step 2: Rearranging the inequality
Move all terms to one side of the inequality: Now, our goal is to prove that this expression is less than 0 for and .
Step 3: Analyzing boundary cases
Before proving it in general, let’s check some specific cases where .
Case 1:
Substitute and into the inequality: Since , the inequality holds for .
Case 2:
Substitute and into the inequality: Since , the inequality holds for .
Step 4: General proof
We will now attempt a general approach. Consider the expression: Since and , observe that grows much faster than , especially as and increase.
To get a clearer picture, rewrite the inequality as follows: Dividing both sides by (which is positive), we get: Now, since when , and this is a strict inequality when , the inequality holds.
Conclusion:
The inequality is true for all and . The term grows much faster than the sum , ensuring that the left-hand side remains smaller than the right-hand side.
Would you like more details on any part of this proof?
Here are 5 related questions for you to consider:
- How would the inequality change if or were less than 1?
- Can you prove this inequality using calculus or derivatives?
- Does this inequality hold for irrational numbers?
- What is the geometric interpretation of this inequality in terms of areas?
- How does this inequality relate to the AM-GM inequality?
Tip: When proving inequalities, testing boundary cases often gives you insights into the general structure of the problem!
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Math Problem Analysis
Mathematical Concepts
Inequalities
Algebra
Quadratic Growth
Formulas
x^2 + y^2 < (xy)^2
Rearranged inequality: x^2 + y^2 - x^2y^2 < 0
Theorems
Quadratic Growth Rate Comparison
Suitable Grade Level
Advanced High School / Early College
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