Why some integers can never be expressed as the sum of two squares

A number theory proof · 10:17 · Video: blackpenredpen · Watch at the source

In short: This video explores a fundamental proof in number theory by investigating whether any integer solutions exist for the equation a^2 + b^2 = 4c + 3. It demonstrates how simple modular arithmetic can rule out possibilities that seem complex at first glance.

The core of the problem lies in understanding the behavior of perfect squares when divided by 4. By examining the remainders (mod 4) of any integer squared, one can determine which values are mathematically possible for the sum a^2 + b^2.

The proof shows that because certain remainders are impossible for individual squares, their sum cannot equal an expression that consistently results in a remainder of 3. This provides a definitive disproof of the existence of integer solutions for the given equation.

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