# Difference between Two Squares equal to Repunit/Examples/R 2

We have that $11$ is a prime.
 $\ds 11$ $=$ $\ds 1 \times 11$ $\ds \leadsto \ \$ $\ds \frac {11 + 1} 2$ $=$ $\ds 6$ $\ds \frac {11 - 1} 2$ $=$ $\ds 5$ $\ds \leadsto \ \$ $\ds 6^2 - 5^2$ $=$ $\ds 36 - 25$ $\ds$ $=$ $\ds 11$
$\blacksquare$