Sigma Percentile
JEE Main 11 Jan 2019 (Evening)
LEVELBoard

Animated Solution for Mathematics - Basic Mathematics: Contrapositive of the statement "If two numbers are not equal, then their squares are not equal." Is:

Select Answer:

Visualized Solution

Identifying the Statement Structure

  • Original Statement: "If two numbers are not equal, then their squares are not equal."
  • Structure: If , then
  • Symbolic form:

Defining the Components and

  • : Two numbers are not equal ()
  • : Their squares are not equal ()

The Rule of Contrapositive

  • Rule: Contrapositive of is
  • Logical equivalence:

Finding Negation of

  • Negation of (): The squares are equal
  • Mathematically:

Finding Negation of

  • Negation of (): The numbers are equal
  • Mathematically:

Constructing the Contrapositive

  • Combining and :
  • Contrapositive: "If the squares of two numbers are equal, then the numbers are equal."

Matching with Options

  • Derived: "If the squares of two numbers are equal, then the numbers are equal."
  • This matches Option A.
  • Key Takeaway:

The Sigma Insight: Linear Inequalities

Analyzing the Architecture of Logic

Welcome, future engineer. Today, we are not just solving a problem; we are peeling back the layers of human thought to understand the very foundation of mathematical reasoning: Logic.
Often, students rush to calculate, but in logic, the beauty lies in the structure. Let us dissect the statement: "If two numbers are not equal, then their squares are not equal."

Deconstructing the Statement

To master this, we must first identify the skeleton. Every conditional statement follows the form "If , then ".
Here, our antecedent is "two numbers are not equal", which we can write as $x eq y$. Our consequent is "their squares are not equal", which we write as $x^2 eq y^2$.
So, our original statement is simply .

The Rule of Contrapositive

Now, the question asks for the contrapositive. This is a specific logical operation. Many students confuse it with the converse or the inverse.
Let us be precise. The contrapositive of is defined as .
This is not just a rearrangement; it is a transformation that preserves the logical integrity of the original statement. It is a powerful tool in proofs because it allows us to approach a problem from a different angle while maintaining the same truth value.

The Process of Negation

To find the contrapositive, we must perform two steps: negate the consequent and negate the antecedent.
First, let us look at : "$x^2 eq y^2$". The negation, , is the exact opposite: "".
Next, we look at : "$x eq y$". The negation, , is "". We have now successfully identified our building blocks.

Synthesis

The Final Statement
Now, we assemble them into the structure . We start with : "If the squares of two numbers are equal".
Then, we follow with : "then the numbers are equal". Putting it together, we get:
"If the squares of two numbers are equal, then the numbers are equal."
This is the contrapositive. It is elegant, it is precise, and it is logically equivalent to the original statement. By mastering this simple "flip and negate" rule, you have unlocked a fundamental technique used in everything from basic algebra to advanced real analysis.

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