Simplifying the Expression: $ S = rac{(a + b)^2 + (a - b)^2}{(a - b)(a + b)} $

Mathematics is full of elegant simplifications, and one particularly insightful expression involves simplifying a compound fraction to reveal its underlying structure. Here, we explore the simplification of:

$$
S = rac{(a + b)^2 + (a - b)^2}{(a - b)(a + b)} = rac{2a^2 + 2b^2}{a^2 - b^2}
$$

Understanding the Context


Step-by-Step Simplification

Step 1: Expand the Numerator

Start with the numerator:
$$
(a + b)^2 + (a - b)^2
$$

Key Insights

Using the identity $(x + y)^2 = x^2 + 2xy + y^2$, expand both squares:

$$
(a + b)^2 = a^2 + 2ab + b^2
$$
$$
(a - b)^2 = a^2 - 2ab + b^2
$$

Now add them:

$$
(a + b)^2 + (a - b)^2 = (a^2 + 2ab + b^2) + (a^2 - 2ab + b^2) = 2a^2 + 2b^2
$$


Final Thoughts

Step 2: Simplify the Denominator

The denominator is:
$$
(a - b)(a + b)
$$

This is a difference of squares:
$$
(a - b)(a + b) = a^2 - b^2
$$


Step 3: Rewrite $S$ with the Simplified Parts

Now substitute both simplified forms back into $S$:

$$
S = rac{2a^2 + 2b^2}{a^2 - b^2}
$$

This matches the given simplified form.


Final Result