What is the proof for the equation x2 + y2 = (x + y) (x – y)?

 There are several ways to prove the equation x² + y² = (x + y)(x – y). Here are two common methods:

Method 1: Expanding the Binomial Product

1. Start with the expression on the right side of the equation: (x + y)(x – y).

2. Expand the parentheses using the distributive property:

   • x(x) + x(-y) + y(x) + y(-y)
   • x² - xy + xy - y²

3. Notice that the middle two terms xy and -xy cancel out each other.

4. Therefore, the expanded expression becomes x² - y², which is exactly the expression on the left side of the equation.

5. Hence, we have proven that x² + y² = (x + y)(x – y) by expanding the binomial product and demonstrating that both sides become identical.

Method 2: Visualizing with the Pythagorean Theorem

1. Consider a right triangle with legs of length x and y and hypotenuse of length √(x² + y²).
2. Apply the Pythagorean theorem to this triangle: x² + y² = (√(x² + y²))².
3. Simplify the right side: x² + y² = x² + y².
4. This demonstrates that both sides of the equation represent the area of the same square, namely the square built on the hypotenuse of the right triangle.
5. Therefore, x² + y² = (x + y)(x – y) is visually proven using the Pythagorean theorem and the concept of area equivalence.

Both methods provide valid proofs for the equation x² + y² = (x + y)(x – y). You can choose the method that best suits your understanding and preferred approach to mathematical concepts.

Remember, proofs in mathematics aim to establish certainty and clarity by demonstrating the logical connection between the given statement and its justification. Feel free to explore other proofs or delve deeper into any specific steps if you need further clarification.