Question

(under root 5-under root 2)(under root 5+under root 2)

Answer 1

Here is your answer

$( \sqrt{5} - \sqrt{2} )( \sqrt{5} + \sqrt{2} ) \\ = ( \sqrt{5} ) {}^{2} - ( \sqrt{2} ) {}^{2} \\ = 5 - 2 \\ = 3$
Hope it helps you

Answer 2

(√5-√2)(√5+√2)
(√5)²-(√2)²
√25-√4
5-2
=3