How do you simplify the expression (sqrt13+sqrt11)(sqrt13-sqrt11)?

$2$
$\left(a + b\right) \left(a - b\right) = {a}^{2} - {b}^{2}$
$\left(\sqrt{13} + \sqrt{11}\right) \left(\sqrt{13} - \sqrt{11}\right) = {\left(\sqrt{13}\right)}^{2} - {\left(\sqrt{11}\right)}^{2} = 13 - 11 = 2$