Simplify $(\sqrt{7} + \sqrt{3})^2 - (\sqrt{7} - \sqrt{3})^2$.

Explanation

1. 01

   $(a + b)^2 - (a - b)^2 = 4ab$.

2. 02

   With $a = \sqrt{7}$, $b = \sqrt{3}$: $4\sqrt{7}\sqrt{3} = 4\sqrt{21}$.

3. 03

   Check by expanding: $(10 + 2\sqrt{21}) - (10 - 2\sqrt{21}) = 4\sqrt{21}$.